don't auto position other floater when it is hosted

Added checks for LLViewerRegion pointer in LLViewerObject being invalid.

Mindful that some autobuild packages populate only packages/lib/release
(rather than packages/lib/debug), Linking.cmake always appends
packages/lib/release to CMake's link_directories() directive. But since CMake
always appends CMAKE_BUILD_TYPE to those directories, we end up with a phantom
packages/lib/release/Release directory on the search path. This would be
harmless except that the Mac's 'ld' command produces a warning. These warnings
quickly make TC's "Important Messages" output useless. Try appending
packages/lib/release only when the build type isn't already Release.

WOLF-363: (partial) correct ordering of cleaning build dir vs running
          'autobuild install'

MAINT-922 FIX Client side code to catch the SCRIPT_PERMISSION_TELEPORT request from similator and display a notification
Reviewed by Simon

Incoming changes from two different project repos left viewer-development with
LLInventoryModel::removeItem() and removeCategory() plus free functions
remove_item() and remove_category() in llinventoryfunctions.cpp.
remove_category() was actually the better implementation; migrated its body
into LLInventoryModel::removeCategory(). Clearly the previous state of affairs
-- with LLInventoryModel::removeItem() plus a remove_category() free function
in a very different source file -- fooled two different developers into
overlooking the other of the pair. Unfortunately we each added different
"missing" functions, leaving us with a complete set of four.
Fix existing references to remove_item() and remove_category() free functions.

Notification handlers now use LLHandles to screen channels.

Fixed boost trackable objects usage.

LL_PATH_USER_SETTINGS. This will allow a common write location for development
and installed configurations. Should correct installed configuration from
permission failures on windows systems where writing to the install directory
requires elevation of rights to administrator.

Subtask of STORM-637