added initial memory usage tracking for lltrace

indra/llcommon/lltrace.cpp

indra/llcommon/lltrace.h

indra/llcommon/lltraceaccumulators.cpp

indra/llcommon/lltraceaccumulators.h

indra/llcommon/lltracerecording.cpp

indra/llcommon/lltracerecording.h

indra/llcommon/lltracethreadrecorder.cpp

indra/llcommon/lltracethreadrecorder.h

indra/llrender/llvertexbuffer.cpp

indra/newview/app_settings/settings.xml

indra/newview/llappviewer.cpp

indra/newview/llviewerobject.cpp

indra/newview/skins/default/xui/en/floater_stats.xml