Unify MachineType and RepType.

MachineType now tracks both the representation and the value type of machine quantities and is used uniformly throughout TurboFan.

These types can now express uint8, int8, uint16, and int16, i.e. signed and unsigned smallish integers. Note that currently only uint8 and uint16 are implemented in the TF backends.

R=bmeurer@chromium.org, mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/470593002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23122 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix MSVC build.

And while we are at it, use the stupid MSVC compiler intrinsics.

TEST=base-unittests/BitTest
TBR=jarin@chromium.org

Review URL: https://codereview.chromium.org/473773003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23123 ce2b1a6d-e550-0410-aec6-3dcde31c8c00