- Make python test runner force COLUMNS=0 to increase determinism.

 - Substitute clang-cc as we do for clang.

 - Improved detection of Ctrl-C.

 - Honor CLANG and CLANGCC environment variables.

 - Add proper command line arguments to TestRunner.py (see --help)

llvm-svn: 73640

llvm-svn: 68814

Usage: from clang/test, 'make -f ../utils/test/Makefile.multi'

Pros: About 20% faster than the Makefile based version on my 8 core
box (way faster on Windows I imagine, if it works).

Cons: Needs some cleanup. Ctrl-C works quite poorly on Darwin; more
Python's fault than mine.

Future: Support config definitions so we can use this for running LLVM
tests instead of dejagnu. Parallel testing goodness? Indeed.

llvm-svn: 66293