Blender Git Loki

Fix T55503: File browser filter not working correctly.

There were two issues here, introduced by rB66aa4af836:
* Forgot to change length of some filter_glob var deep in filebrowser code.
* Truncating filter_glob in general can be dangerous, generating
unexpected patterns.

Last point was the root of the issue here, truncating to 63 chars string
left last group as 'match everything' `*` pattern.

To fix that to some extent, added a new BLI_path_extension_glob_validate
helper to BLI_path_util, which ensures we do not have last
wildcards-only group in our pattern, when there are more than one group.