SL-11727 Fix build warnings

doc/contributions.txt

indra/llaudio/llaudiodecodemgr.cpp

indra/llcommon/llsdserialize.cpp

indra/llcorehttp/_httpservice.cpp

indra/llcorehttp/bufferarray.cpp

indra/llimage/llimagejpeg.cpp

indra/llimage/llpngwrapper.cpp

indra/llmath/llvolume.cpp

indra/llmessage/llcorehttputil.cpp

indra/llmessage/llhttpnode.cpp

indra/newview/llappviewer.cpp

indra/newview/llmeshrepository.cpp

indra/newview/llsecapi.cpp