Firefox 27 and nss 3.15.4

xulrunner wanted the newer version of nss

I made firefox's preConfigure cd to a subdirectory, because otherwise I saw the following message:

  ***
  * Building directly in the main source directory is not allowed.
  *
  * To build, you must run configure from a separate directory
  * (referred to as an object directory).
  *
  * If you are building with a mozconfig, you will need to change your
  * mozconfig to point to a different object directory.
  ***