Instead of trying to expand whole range at regcomp() stage as we do,
GNU regex allocates separate ranges [start,end] set each character
is checked against, so collation is possible and turned on for ranges here.
When something like that will be implemented or our obsoleted regex code
will be replaced to something like TRE, and in case we decide to use
collation in [a-z] ranges, all changes related to r302512 can be backed out,
but now we need consistency.
f04b8af8fa