new_compiler takes "compiler" as a compiler name. It would make much
sense to make it accept a compiler instance.

now for people setup.py, I wasn't aware that people are using
build_ext.compiler as a compiler, besides Python itself.

IMHO we should rename the compiler option to "compiler_type" then
provide an API build_ext.get_compiler() then fix Python setup.py file.

Then this should not go into 2.6 but in 2.7, and we should put back the
option in new_compiler like it was (it's wrong but at least it works if
you run the command just once, which is the most common case)