Bug fix in LLPreviewAnim::gotAssetForSave_continued: the if()
that tests if the result from the filepicker can be used was
accidently negated, mostly causing a crash when cancelling an
animation preview download (open animation, File -> Save Texture As..),
and canceling the save when a filename is picked.
The lifetime of AIFileUpload is actually till the very end
of the main(), causing it's member mPicker to be reused.
This leads to problems. When someone tries to open a file picker
for a file upload of the same time before the previous filepicker
called the callback function (ie, when two filepickers are
opened at the same time, or when the plugin crashes).
With this fix it is possible to open any number of file pickers.
Finally, for linux, LLFastTimers was using assembly with gives
rather random results on multicore machines. Since AIStateMachine
is using this for wait timing, it had a negative effect on
how well the file picker worked (the last message wasn't flushed
for several seconds).
