Fixed behaviour of make -k if there is an error in a subdirectory

Fixed behaviour of make -k if there is an error in a subdirectory

The previous implementation of recursive invocation of make in
subdirectories didn't obey the -k flag. If there was an error in some
subdirectory, the other directories were not made.

This patch creates a separate targets for each subdirectory and pass and
add them as a dependencies to the main pass target. This way the
compilation errors are handled correctly with the -k flag.

darcs-hash:20080417062508-f2ef6-d049eff642e8c33ee1822d8b321bf1365ed80869.gz