Update Test::Harness usage for Test-Harness-3*

Test-Harness-2 and older directly executed testcases that did not end in .t.
In version 3, this is no longer the case, and Test::Harness is now a thin
wrapper around TAP::Harness. To make the testcases work again, we introduce a
subclass of TAP::Harness, that allows direct execution where needed.

Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

--- mysql/unittest/unit.pl.orig	2011-04-17 18:12:47.104981268 +0000
+++ mysql/unittest/unit.pl	2011-04-17 19:05:46.520096987 +0000
@@ -93,7 +93,23 @@
         # Removing the first './' from the file names
         foreach (@files) { s!^\./!! }
         $ENV{'HARNESS_PERL_SWITCHES'} .= q" -e 'exec @ARGV'";
+        $ENV{'HARNESS_SUBCLASS'} = qw(TAP::Harness::Exec);
         runtests @files;
     }
 }
 
+package TAP::Harness::Exec;
+use base qw(TAP::Harness);
+sub new {
+    my ($class, $arg_for ) = @_;
+    $arg_for ||= {};
+    $arg_for->{exec} = sub {
+        my ( $harness, $test_file ) = @_;
+        return undef if $test_file =~ /[.]t$/;
+        return [ $test_file ] if -x $test_file;
+        # This is a failure now
+        return undef;
+    };
+    return $class->SUPER::new( $arg_for );
+}
+1;