_GCC_LIMITS_H_ is defined, when __GNUC__ is defined.
Also, we need to stay away from possible conflicts with header guards.
We should use CLANG_ to prefix all header guards.
llvm-svn: 64408
don't typecast CHAR_MIN to char, this makes it not a PP constant
and gives it the wrong unpromoted type. Thanks to Sebastian for
pointing this out!
llvm-svn: 63980