Misc cleanup of strings, const ref, and container emplacement

indra/llmath/llcamera.cpp

indra/llmath/lloctree.h

indra/llmath/llvolume.cpp

indra/llmath/llvolume.h

indra/llmath/llvolumemgr.cpp

indra/llmath/m3math.cpp

indra/llmath/m4math.cpp

indra/llmath/raytrace.cpp

indra/llmath/raytrace.h

indra/llmessage/llavatarname.cpp

indra/llmessage/llavatarnamecache.cpp

indra/llmessage/llcachename.cpp

indra/llmessage/llchainio.h

indra/llmessage/llhost.cpp

indra/llmessage/lliohttpserver.cpp

indra/llmessage/message.cpp