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

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/script.js converts a UNIX timestamp into the local date/time

 - http/example.config.inc.php 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