The folder where the disk cache lives was originally renamed from llvfs to llcache but @henri's suggestion that that doesn't reflect the other files in the same place and it should be llfilesystem is a good one so I changed it over

Renamed the references to LLVFile and llvfile.* source code plus cmake scripts to use a different name - lldiskcache - since that more closely resembles what it is (or will be) now that the VFA is no more

First part of change to remove LLVFS from the Viewer. Consists of code changes to remove LLVFS and LLVFSThread classes along with the associated source files. The existing llvfs folder is renamed to llcache. Also includes changes to CMake script in many places to reflect changes. Eventually, llvfile source file and class will be renamed but that is not in this change.

Effective rename of DRTVWR-506-simple since there is no way to rename a branch. Cloned canonical viewer into DRTVWR-519, copied over the files that changed from DRTVWR-506-simple and pushed back.  Once I am satisfied everything is correct, DRTVWR-506-simple will be removed

following promotion of DRTVWR-501

to reflect previous commit and use correct pool size

following promotion of DRTVWR-476

This reverts commit bf999f2f due to revert of updater, this will be moved to separate 'epic' instead

This fails at teamcity due to missing LLTrans, but builds locally without issues. Reverting to not hold D501

This reverts commit 31d9930a.

Nat's suggested improvement to LLThreadSafeQueue that takes account of queue being empty as well as the status flag condition

Get rid of that ugly '#pragma clang diagnostic ignored "-Wdelete-incomplete"' by making sure the delete always happens inside llview.cpp, where the type of LLView is known.

Updated nghttp2 to codeticket version 545354
Updated boost to codeticket version 545361
Updated colladadom to codeticket version 545362
Updated googlemock to codeticket version 545363
Updated curl to codeticket version 545369

LLExtStat had been a S32, this wasn't right, as some of the constants lead to integer overflow: const LLExtStat LL_EXSTAT_RES_RESULT = 2L<<30; const LLExtStat LL_EXSTAT_VFS_RESULT = 3L<<30; This shifts into the sign bit and clang gets (rightfully) upset about this.

LLExtStatus needs to be at least of type U32 to remedy this problem, but
while at it it makes sense to turn it into what it is: An enum. Turning
it into a class enum has the added benefit we get type safety for mostly
free.
Which incidentally turned up a problem right away:
A call to removeAndCallbackPendingDownloads had status and extstatus
reversed and thus was wrong.

There was an idiom to test with LL_DARWIN if the compiler used is clang. This is not correct, as clang is available on all 3 platforms. The correct way to check for this is via __clang__ (https://clang.llvm.org/docs/LanguageExtensions.html#builtin-macros)

# Conflicts:
#	autobuild.xml
#	indra/newview/llimprocessing.cpp

following promotion of DRTVWR-476