Do not alter match data in Fcapitalize etc.

Do not alter match data in Fcapitalize etc.

Without this patch, (capitalize "x") can alter the match data,
which is not what users expect.  Problem found by running
morse-tests-unnato-region in a stripped-down Emacs.
Perhaps ‘load’ should also save and restore the match data?
That would be a simpler fix, though arguably incompatible.
* src/lread.c (save_match_data_load): New function.
* src/chartab.c (uniprop_table):
* src/doc.c (reread_doc_file):
* src/eval.c (Fautoload_do_load):
* src/fns.c (Frequire): Use it.