Parse GL3.txt into XML

New files:
 - scripts/setup.php clones the Mesa git repository into the required location
 - scripts/parse.php parses docs/GL3.txt into an XML file
 - scripts/git.inc.php contains helpers for dealing with the external git
   command
 - scripts/fetch.php updates the Mesa git clone

Changes:
 - http/index.php reads the XML file and constructs the HTML from it
   footnote section at the bottom has been removed due to technical limitations
 - http/oglparser.inc.php has been moved to scripts, and now has the ability
   to read directly from a stream or from a string
 - http/commitsparser.inc.php has been moved to scripts
 - http/script.js converts a UNIX timestamp into the local date/time

 - http/example.config.inc.php has been moved to the root, and has several
   changes:
    * chdir into root directory (containing http, scripts etc) so that all
      defined paths can be relative to that
    * new section ["git"] containing settings for the Mesa git repository
    * removed section ["auto_fetch"]
    * new key ["info"]["xml_file"]
Move author definitions into config.inc.php
Move $config to static member of class

Fixes all global variable scope issues, refer to $config as MesaMatrix::$config

debug_print is now a static member function of MesaMatrix too
Create new directory structure

The following directory structure is used:
 - http/  Files accessible by web server: JS, CSS, index.php, gl3.xml
 - lib/   Class files, included by other files
 - tools/ Tools to be run on the command line

All include files have had the .inc.php suffix dropped for just .php