Upgrade LLVM to release 2.3.
In theory this should build on every architecture so remove the
Add a MAINTAINER_MODE option to allow debug (very slow) versions to be built
and a regression-test target. 
Submitted by: Pedro Giffuni <pfgshield dash freebsd at yahoo dot com> 
Upgrade devel/llvm and lang/llvm-gcc4 to LLVM 2.2.
Switch llvm-gcc4 from the deprecated gcc 4.0 based version to a new gcc
4.2 based release.
See the release notes for details: