Fix implementation of bit count functions.
The bit counting functions provided by CompilerIntrinsics were undefined
for zero, which was easily overlooked and unsafe in general. Also their
implementation was kinda hacky and mostly untested. Fixed the
implementation and moved the functions to base/bits.h.
TEST=base-unittests,cctest,compiler-unittests,mjsunit
R=hpayer@chromium.org
Review URL: https://codereview.chromium.org/
494633002
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23229
ce2b1a6d-e550-0410-aec6-
3dcde31c8c00