[AVX512] Add parentheses around macro arguments in AVX512BW intrinsics. Remove...

[AVX512] Add parentheses around macro arguments in AVX512BW intrinsics. Remove leading underscores from macro argument names. Add explicit typecasts to all macro arguments and return values. And finally reformat after all the adjustments.

This is a mostly mechanical change accomplished with a script. I tried to split out any changes to the typecasts that already existed into separate commits.

llvm-svn: 269739