Converts a string into a collation key that can be compared with other collation keys produced by the same function using strcmp.
In order to sort filenames correctly, this function treats the dot '.' as a special case. Most dictionary orderings seem to consider it insignificant, thus producing the ordering "event.c" "eventgenerator.c" "event.h" instead of "event.c" "event.h" "eventgenerator.c". Also, we would like to treat numbers intelligently so that "file1" "file10" "file5" is sorted as "file1" "file5" "file10".
Note that this function depends on the current locale.
a UTF-8 encoded string.
a newly allocated string. This string should be freed with g_free when you are done with it.