Squashed commit of the following:

commit ef1a217bbb2b0abd21a630e6154ff8dc5e968caa
Author: Romain Courteaud <romain@nexedi.com>
Date:   Tue Oct 11 10:01:10 2011 +0200

    Escape $$ character to $.

    Do not escape when fetching dependency values.

commit 8232c9aa4e4906f67e0b6ca5fd8a9f09d05f315f
Author: Antoine Catton <acatton@tiolive.com>
Date:   Mon Oct 10 09:57:12 2011 +0200

    Add tests for dollar sign escaping