Enable 'm' flag on regex for multi-line tests

This is a change to the multi-line match option to enable traditional regex multi-line matching. The m flag causes ^ and $ to actually match correctly on new line/carriage returns, where before the match was actually on the entire file so ^ was just beginning of file $ was the end. This also fixes a few tests' failure condition where this subtle difference wasn't noticed and '^warning: ignoring' is used.

regression/test.pl

@@ -174,7 +174,7 @@ ($$$$$$$$$)
             binmode $fh;
             my $whole_file = <$fh>;
             $whole_file =~ s/\r\n/\n/g;
-            my $is_match = $whole_file =~ /$result/;
+            my $is_match = $whole_file =~ /$result/m;
             $r = ($included ? !$is_match : $is_match);
           }
           else