Adjust script detection rules to work with file >= 5.07 too (RhBug:712251)

Adjust script detection rules to work with file >= 5.07 too (RhBug:712251)
- Somewhere between file 5.05 and 5.07 it started adding encoding
  to script descriptions, eg "<mumble> script text executable" became
  "<mumble> script, <encoding> text executable" breaking what had
  been working for 10+ years in the case of old find-requires.
- Permit either comma or space after "script", this works for both
  old and new file.