Errors from the DBD Parser should stop dbdExpand

Such errors used to be just warnings, now they stop the output
file being generated unless the -D flag was given.

src/tools/dbdExpand.pl

@@ -44,6 +44,7 @@ while (@ARGV) {
         warn "  Your Makefile may need this dependency rule:\n" .
             "    $dep: \$(COMMON_DIR)/$file\n"
             if $@ =~ m/Can't find file/;
+        exit 1 unless $opt_D;
     }
 }