Fix some signed/unsigned warnings

indra/llappearance/llwearable.cpp

indra/llcommon/StackWalker.cpp

indra/llimage/llimage.cpp

indra/llrender/llfontfreetype.cpp

indra/newview/lldrawable.cpp

indra/newview/llfloatereditdaycycle.cpp

indra/newview/llfloaterexperiences.cpp

indra/newview/llinventorymodel.cpp

indra/newview/llpanelgrouproles.cpp

indra/newview/llteleporthistory.cpp

indra/newview/lltexturefetch.cpp

indra/newview/llviewerobjectlist.cpp

indra/newview/llviewerwearable.cpp

indra/newview/llvocache.cpp