tm_tags_find() relies on a sorted tags array to be passed in but in
tm_source_file_set_tag_arglist() we don't have a sorted array yet and
sorting it on demand seems more heavy than the alternative:
make tm_tags_find() search the array linear if the new flag is set.

This fixes a bug in the Python parser when assigning the argument list
of __init__() methods to their class' argument list which annoyed me
for years already.

Also add a test case for this.