Fix #13793. Correct source map generation bugs.

Ticket: http://bugs.jquery.com/ticket/13793

I **really** need people to test it, this all is way too fragile.

There were a few errors:
1) The jquery.jq -> jquery.pre-min.js modification changed the number of banner text lines which broke source map references.
2) The jquery.min.map file referenced to jquery.pre-min.js instead of jquery.js.
3) File references in jquery.min.map had "dist/" preprended.

I tested all those files in Chrome and via http://sokra.github.io/source-map-visualization/ (a great tool btw) and it seems at the beginning of the file everything is now OK but it breaks near the end. Maybe there's a bug in UglifyJS?