gmtime and gmtime_r share the same common code. They call gmtime_internal
a static inline function. Thus added only validation tests for gmtime_r.
Reviewed By: sivachandra
Differential Revision: https://reviews.llvm.org/D99046
This change doesn't handle TIMEZONE, tm_isdst and leap seconds.
Moved shared code between mktime and gmtime into time_utils.cpp.
Reviewed By: sivachandra
Differential Revision: https://reviews.llvm.org/D98467