[clang-tidy] Add "portability" module and rename readability-simd-intrinsics...

[clang-tidy] Add "portability" module and rename readability-simd-intrinsics to portability-simd-intrinsics

Reviewers: alexfh

Subscribers: klimek, nemanjai, mgorny, xazax.hun, kbarton, cfe-commits

Differential Revision: https://reviews.llvm.org/D44173

llvm-svn: 326909