Mark Pascal as case-insensitive

The Pascal language is not case-sensitive, so implement the
appropriate language method.  This fixes gdb.pascal failures with
-gw3.

I wasn't sure if -gw3 should be the default so I've left it as-is.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33617
Approved-By: Tom de Vries <tdevries@suse.de>