Merge branch 'lindenlab/release' (6.4.18) into viewer/build

autobuild.xml

doc/contributions.txt

indra/cmake/Copy3rdPartyLibs.cmake

indra/cmake/URIPARSER.cmake

indra/llcommon/llcoros.cpp

indra/llcommon/llexception.cpp

indra/llcommon/llexception.h

indra/llcommon/llsingleton.cpp

indra/llcommon/llsys.cpp

indra/llcommon/lluriparser.cpp

indra/llcommon/lluriparser.h

indra/llcorehttp/CMakeLists.txt

indra/llmessage/llassetstorage.h

indra/llmessage/llavatarnamecache.cpp

indra/llmessage/llcoproceduremanager.cpp

indra/llmessage/llcoproceduremanager.h

indra/llprimitive/llmaterial.cpp

indra/llprimitive/llmaterial.h

indra/llui/llcheckboxctrl.cpp

indra/llui/llfolderviewmodel.h