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>

gdb/p-lang.h

@@ -154,6 +154,9 @@ public:
   bool range_checking_on_by_default () const override
   { return true; }
 
+  enum case_sensitivity case_sensitivity () const override
+  { return case_sensitive_off; }
+
 private:
 
   /* Print the character C on STREAM as part of the contents of a literal