Commit 093cc00cdd9d8cf31ecce5bc1dd3645c460a1b98 sets the CPP environment
variable by default, confusing the newt Makefile, which expects CPP=gcc for
computing dependencies.
I add newt, checking that it cross-builds too.
I update perf to have newt support, and now it's also finding python, whatever
that means. I've not tested if 'python' as buildInputs is enough.
svn path=/nixpkgs/trunk/; revision=31353