[clang-tidy] misc-argument-comment non-strict mode

Summary:
The misc-argument-comment check now ignores leading and trailing underscores and
case. The new `StrictMode` local/global option can be used to switch back to
strict checking.

Add getLocalOrGlobal version for integral types, minor cleanups.

Reviewers: hokein, aaron.ballman

Subscribers: aaron.ballman, Prazek, cfe-commits

Differential Revision: https://reviews.llvm.org/D23135

llvm-svn: 277729