add --tags to 'git describe'

'git describe' calculates the version since the last **annotated** diff. Adding --tags shows the most recent tags (v0.94, for example) regardless if they're annotated or not.

lib/Qpsmtpd.pm

@@ -16,7 +16,7 @@ my $git;
 
 if (-e ".git") {
     local $ENV{PATH} = "/usr/bin:/usr/local/bin:/opt/local/bin/";
-    $git = `git describe`;
+    $git = `git describe --tags`;
     $git && chomp $git;
 }