This reverts commit b45c0e3e.

SL-17074 Redo ALT-F4 handling fix

Merged previewAvatar and generateImpostor into a single function since they are nearly identical

SL-17000 improve error message for physics mesh import

SL-17077 Ensure profiling is disabled if gpu_benchmark fails.  Log the source of the real crash for when the viewer inevitably crashes later.

SL-16993

Approved-by: Euclid Linden

SL-17028 Fix for inconsistent ordering of transparent rigged meshes and removal of glow-only rigged meshes from depth buffer.

SL-17074 Fix Alt-F4 handling bug

Might be a better idea to turn LLWorld back into an LLSingleton. Too many things to track.

When animesh stops being an animesh it might still be in a list, but will no longer have an avatar

More DRTVWR-550 Teamcity build fix. another piece of python2 syntax leftover in an error handling block