[Diagnostics] Support -Wtype-limits for GCC compatibility

Summary:
GCC's  -Wtype-limits (part of -Wextra):
Warn if a comparison is always true or always false due to the limited range of the data type

Reviewers: rsmith, aaron.ballman, lebedev.ri, thakis

Reviewed By: rsmith

Subscribers: lebedev.ri, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58841

llvm-svn: 359516