Fix enum bug in module legacy namespace.

[nbeloglazov]

[nbeloglazov]

Actually hold on. I think the bug is not fixed. Clutz produces different output depending on goog.module name I just got lucky in the test.

[nbeloglazov]

Ready for review.

[rkirov]

Can you rebase, this looks good.

[nbeloglazov]

This change doesn't work in one case like:

goog.module('foo');

const bar = goog.require('bar');

/** @enum {number} */
const Color = bar.Color;
exports.Color = Color;

where bar is coming from another module (so its source is not processed by Clutz). Need to figure out how it should be handled.