Fix lerp conflict with GCC 11

indra/llcharacter/llmotion.cpp

indra/llcommon/lltracerecording.cpp

indra/llinventory/llsettingsbase.cpp

indra/llinventory/llsettingssky.cpp

indra/llmath/llmath.h

indra/llmath/llvolume.cpp

indra/llrender/llrender2dutils.cpp

indra/llui/llbutton.cpp

indra/llui/llfloater.cpp

indra/llui/llfocusmgr.h

indra/llui/llfolderviewitem.cpp

indra/llui/lllayoutstack.cpp

indra/llui/llmenugl.cpp

indra/llui/llscrollbar.cpp

indra/llui/llstatbar.cpp

indra/llui/lltabcontainer.cpp

indra/llui/llviewborder.cpp

indra/newview/llagentcamera.cpp

indra/newview/llagentpilot.cpp

indra/newview/llfasttimerview.cpp