Initial translation of the c version of jsmin to go.

This is just an initial translation of the original c code (https://github.com/douglascrockford/JSMin/blob/master/jsmin.c).

The original js and the minified one used in in the test are taken from http://www.crockford.com/javascript/jsmin.html.

One thing to double check is the use of `fallthrough`, which is not used in the c library because it's the default behaviour of the switch statement in c.