python-gyp: Update to SVN revision 1738.

This fixes a few issues with symlinks and also needs to be up to date
because we're going to use it for building Chromium instead of the
bundled GYP that comes with Chromium.

Also, the package was missing a license and in the current revision, we
also have test cases, so let's enable them.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>