merge changes for 2.7.4 release

.hgtags

BuildParams

autobuild.xml

doc/contributions.txt

indra/llcommon/llaccountingquota.h

indra/llcommon/llsdserialize.cpp

indra/llcommon/llstat.cpp

indra/llcommon/llsys.cpp

indra/llcommon/llversionviewer.h

indra/llmath/lloctree.h

indra/llmath/llvolume.cpp

indra/llmath/llvolume.h

indra/llmessage/message_prehash.cpp

indra/llmessage/message_prehash.h

indra/llmessage/tests/commtest.h

indra/llmessage/tests/test_llsdmessage_peer.py

indra/llmessage/tests/testrunner.py

indra/llprimitive/llmodel.cpp

indra/llprimitive/llmodel.h

indra/llrender/llgl.cpp