send-email: accept absolute path even on Windows

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

git-send-email.perl

@@ -984,7 +984,7 @@ X-Mailer: git-send-email $gitversion
 
 	if ($dry_run) {
 		# We don't want to send the email.
-	} elsif ($smtp_server =~ m#^/#) {
+	} elsif ($smtp_server =~ m#^/# || $smtp_server =~ m#[a-zA-Z]\:#) {
 		my $pid = open my $sm, '|-';
 		defined $pid or die $!;
 		if (!$pid) {