Add inline comments for dynamically created methods

This patch adds inline comments for dynamically created methods. It is inspired by the style in wycats' http://github.com/rails/rails/co...>

There was a first attempt through docrails but some comments got too wide. After some feedback from lifo and other fellows in IRC this second attempt has a few format exceptions for otherwise too wide comments, shorts a few long lines here and there, cuts standard distance from 5 to 2 spaces, and is even more comprehensive.