Implement #pragma clang restrict_expansion

This patch adds `#pragma clang restrict_expansion ` to enable flagging
macros as unsafe for header use. This is to allow macros that may have
ABI implications to be avoided in headers that have ABI stability
promises.

Using macros in headers (particularly public headers) can cause a
variety of issues relating to ABI and modules. This new pragma logs
warnings when using annotated macros outside the main source file.

This warning is added under a new diagnostics group -Wpedantic-macros

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D107095