charset: fix str[n]casecmp_m() by comparing lower case values

charset: fix str[n]casecmp_m() by comparing lower case values

The commits c615ebed6e3d273a682806b952d543e834e5630d^..f19ab5d334e3fb15761fb009e5de876dfc6ea785
replaced Str[n]CaseCmp() by str[n]casecmp_m().

The logic we had in str[n]casecmp_w() used to compare
the upper cased as well as the lower cased versions of the
characters and returned the difference between the lower cased versions.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13018

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Fri Sep 15 02:23:29 CEST 2017 on sn-devel-144

(cherry picked from commit 3ed9c903671e795964ce3da9d0080444ef3eb5e9)