Unfinished typing start/stop detection

settings_sliver.xml
->Added bool for announce weird typing stops
->Added bool (unimplemented) for incoming IM session key announce
->Added bool for incoming IM session message announce in addition to key
(unimplemented)
-> Added U32 for incoming IM session message announce channel set

llViewerMessage.cpp:
->Removed a few checks for lindens not being able to be muted.
->added some comments
->added detection for typing stops and starts that the im window can
see, needs some finishing
->todo: implement chat hooks for incoming ims
->todo: toggle for busy auto response capable of infinity loop
->todo: fix the long stack of while loops because they're bad
->moved the part where it fills in the buffer up slightly

Strings.xml:
->added sliver typing start detect string

Updated vcFloaterGNR to match GTS' latest version