merge changes for DRTVWR-439

doc/contributions.txt

indra/llcommon/llsdserialize.cpp

indra/llcommon/llstring.h

indra/llimage/llimagepng.cpp

indra/llimage/llpngwrapper.cpp

indra/llimage/llpngwrapper.h

indra/llmessage/lltemplatemessagereader.cpp

indra/llplugin/llpluginclassmedia.cpp

indra/llrender/llvertexbuffer.cpp

indra/llui/llaccordionctrltab.cpp

indra/llui/llfolderview.cpp

indra/llui/llfolderview.h

indra/llui/llfolderviewitem.cpp

indra/llui/llmenugl.cpp

indra/llui/llnotifications.cpp

indra/llui/llnotifications.h

indra/llui/llnotificationtemplate.h

indra/llui/llscrolllistctrl.cpp

indra/llui/llscrolllistctrl.h

indra/llui/llspinctrl.cpp