compiler info in kernel identification string

Hello,

avg_at_ suggested to include compiler version in the kernel so that it's
present in uname (and one can easly tell what was used to compile it).

Here is my attempt:
http://people.freebsd.org/~mjg/patches/newvers-compiler.diff

Basically adds compiler name and version/revision after revision of
system sources.

Sample output from dirty git sources:
gcc:
FreeBSD 10.0-CURRENT #7 r242962=264d569-dirty(gcc-4.2.1-20070831): Wed
Nov 14 00:11:51 CET 2012

clang:
FreeBSD 10.0-CURRENT #8 r242962=264d569-dirty(clang-r162107): Wed Nov 14
00:12:26 CET 2012

Sample output from svn with gcc:
FreeBSD 10.0-CURRENT #1 r243006:243007M(gcc-4.2.1-20070831): Wed Nov 14
00:41:23 CET 2012

I have no strong opinions on format, I just want this information easly
accessible.

Comments?

-- 
Mateusz Guzik <mjguzik gmail.com>