Eliminate string copies from LLTextBase getText

indra/llprimitive/llmediaentry.h

indra/llui/llaccordionctrltab.cpp

indra/llui/llaccordionctrltab.h

indra/llui/llcheckboxctrl.cpp

indra/llui/llcheckboxctrl.h

indra/llui/llcombobox.cpp

indra/llui/lldraghandle.cpp

indra/llui/lldraghandle.h

indra/llui/llfolderviewitem.cpp

indra/llui/lltextbase.cpp

indra/llui/lltextbase.h

indra/llui/lltimectrl.cpp

indra/newview/llexpandabletextbox.h

indra/newview/llfloaterimnearbychat.cpp

indra/newview/llfloaterimnearbychat.h

indra/newview/llvoicevivox.h