[clang-tidy/google-runtime-int] Allow passing non-bitwidth types to printf()-style APIs

Summary:
The `google-runtime-int` check currently fires on calls like:

  printf("%lu", (unsigned long)foo);

However, the style guide says:

> Where possible, avoid passing arguments of types specified by
> bitwidth typedefs to printf-based APIs.

http://google.github.io/styleguide/cppguide.html#64-bit_Portability

This diff relaxes the check to not fire on parameters to functions
with the `__format__` attribute. (I didn't specifically check
for `__printf__` since there are a few variations.)

Test Plan: New tests added. Ran tests with:
  % make -j16 check-clang-tools

Reviewers: alexfh, bkramer

Reviewed By: alexfh

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D46293

llvm-svn: 331268