Now that the viewer's own background updater logic is responsible for
downloading a new installer, the only functionality we still use in
linux-updater that couldn't be expressed more simply in bash is the UI. But
since most Linux distros capable of running SL at all have zenity, and all
will have xmessage, we can handle even the UI part. Add xmenity wrapper script
so update_install doesn't have to care which is present, and make the bash
script that used to launch linux-updater do the real work.

In a number of different places, for different reasons, the viewer wants to
load a UI-related file that might be overridden by a non-default skin; and
within that skin, might further be overridden by a non-default language.
Apparently, for each of those use cases, every individual developer approached
it as an entirely new problem, solving it idiosyncratically for that one case.
Not only is this a maintenance problem, but it rubs one's nose in the fact
that most such solutions consider only a subset of the relevant skin
directories.
Richard and I evolved an API intended to address all such cases: a central
LLDir method returning a list of relevant pathnames, from most general to most
localized, filtered to present only existing files; plus a couple of
convenience methods to specifically obtain the most general and most localized
available file.
There were several load-skinned-file methods (LLFloater::buildFromFile(),
LLPanel::buildFromFile() and LLUICtrlFactory::createFromFile() -- apparently
cloned-and-modified from each other) that contained funky bolted-on logic to
output the loaded data to an optional passed LLXMLNodePtr param. The trouble
is that passing that param forced each of these methods to subvert its normal
search: specifically for that case, it needed to find the baseline XML file
instead of the localized one. Richard agreed that for the intended usage
(reformatting XML files) we should use XML schema instead, and that the hacky
functionality should be removed. Remove it. Also remove
LLUICtrlFactory::getLocalizedXMLNode(), only used for those three special cases.
Some callers explicitly passed the optional LLXMLNodePtr param as NULL. Remove
that.
Remove LLFloaterUIPreview::displayFloater(save) param, which relied on the
optional output LLXMLNodePtr param. Make onClickSaveFloater() and
onClickSaveAll() emit popupAndPrintWarning() about discontinued functionality.
Recast LLFloater::buildFromFile(), LLPanel::buildFromFile(),
LLUICtrlFactory::createFromFile(), LLNotifications::loadTemplates(),
LLUI::locateSkin(), LLFontRegistry::parseFontInfo(),
LLUIColorTable::loadFromSettings(), LLUICtrlFactory::loadWidgetTemplate(),
LLUICtrlFactory::getLayeredXMLNode(), LLUIImageList::initFromFile(),
LLAppViewer::launchUpdater() and LLMediaCtrl::navigateToLocalPage() to use
findSkinnedFilenames(). (Is LLAppViewer::launchUpdater() ever called any more?
Apparently so -- though the linux-updater.bin logic to process the relevant
command-line switch has been disabled. Shrug.) (Is
LLMediaCtrl::navigateToLocalPage() ever used?? If so, why?)
Remove LLUI::setupPaths(), getXUIPaths(), getSkinPath() and
getLocalizedSkinPath(). Remove the skins/paths.xml file read by setupPaths().
The only configuration it contained was the pair of partial paths "xui/en" and
"xui/[LANGUAGE]" -- hardly likely to change. getSkinPath() specifically
returned the first of these, while getLocalizedSkinPath() specifically
returned the second. This knowledge is now embedded in findSkinnedFilenames().
Also remove paths.xml from viewer_manifest.py.
Remove injected xui_paths from LLFontGL::initClass() and
LLFontRegistry::LLFontRegistry(). These are no longer needed since
LLFontRegistry can now directly consult LLDir for its path search. Stop
passing LLUI::getXUIPaths() to LLFontGL::initClass() in LLViewerWindow's
constructor and initFonts() method.
Add LLDir::append() and add() methods for the simple task of combining two
path components separated by getDirDelimiter() -- but only if they're both
non-empty. Amazing how often that logic is replicated. Replace some existing
concatenations with add() or append().
New LLDir::findSkinnedFilenames() method must know current language. Allow
injecting current language by adding an LLDir::setSkinFolder(language) param,
and pass it where LLAppViewer::init() and initConfiguration() currently call
setSkinFolder(). Also add LLDir::getSkinFolder() and getLanguage() methods.
Change LLFLoaterUIPreview's LLLocalizationResetForcer helper to "forcibly
reset language" using LLDir::setSkinFolder() instead of LLUI::setupPaths().
Update LLDir stubs in lldir_stub.cpp and llupdaterservice_test.cpp.
Add LLDir::getUserDefaultSkinDir() to obtain often-overlooked possible skin
directory -- like getUserSkinDir() but with "default" in place of the current
skin name as the last path component. (However, we hope findSkinnedFilenames()
obviates most explicit use of such individual skin directory pathnames.)
Add LLDir unit tests for new findSkinnedFilenames() and add() methods -- the
latter exercises append() as well.
Tweak indra/integration_tests/llui_libtest/llui_libtest.cpp for all the above.
Notably, comment out its export_test_floaters() function, since the essential
LLFloater::buildFromFile(optional LLXMLNodePtr) functionality has been
removed. This may mean that llui_libtest.cpp has little remaining value, not
sure.

It appears that the LLTrans machinery, or at least the way it's used in this
program, is buggy: linux-updater.bin has been crashing. Tracebacks and
experimentation identify LLTrans as the culprit, so replace it with baked-in
string constants copied from strings.xml. (linux-updater.bin was already
producing English-only messages because the update_install shell script that
calls it was specifically passing the English version of strings.xml.)

Encountering such a mask will show a warning message and throw a debug assertion.

- Replaced all existing usages of LLDir::getNextFileInDir() with the new directory iterator object.
- Removed platform specific LLDir::getNextFileInDir() implementation.

--HG--
branch : storm-102

- Updated linux_updater for new LLStringUtil::getTokens() signature
- Ignore compiler warning for string constants not being referred to
  as const in fmod_error.h

Fix for DEV-39457. Reviewed by moss.

QAR-1771  Linux Viewer Autoupdater + XUI-parse refactoring