New PassManager

Hi All,

I have enabled new pass manager. At this point, it is a replacement for current
pass manager without adding any new features. If you run into any issues then
let me know. Meanwhile to re-enable old pass manager, just uncomment
#define USE_OLD_PASSMANAGER in include/llvm/Pass.h

If the new pass manager does not cause any regression then I will
start removing old manager after few days.