Add a gimp-register-file-handler-priority procedure, which can be
used to set the priority of a file-handler procedure. When more
than one file-handler procedure matches a file, the procedure with
the lowest priority is used; if more than one procedure has the
lowest priority, it is unspecified which one of them is used. The
default priority of file-handler procedures is 0.
Add the necessary plumbing (plus some fixes) to the plug-in manager
to handle file-handler priorities. In particular, use two
different lists for each type of file-handler procedures: one meant
for searching, and is sorted according to priority, and one meant
for display, and is sorted alphabetically.
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