Enable spl autoload of civi classes

This patch will autoload any CRM_ classes as needed, without the random "require_once" statements.

Note that global functions like "ts()" are not autoloaded, so those source files still must be included manually.

Also, this patch will break any other custom autoloaders which expect to load classes beginning with "CRM_", how's that for a namespace conflict?

http://svn.civicrm.org/civicrm/branches/trunk.autoload