libstdc++: Test C++11 implementation of std::chrono::__detail::ceil

libstdc++: Test C++11 implementation of std::chrono::__detail::ceil

Commit 53ad6b1979f4bd7121e977c4a44151b14d8a0147 split the implementation
of std::chrono::__detail::ceil so that when compiling for C++17 and
later std::chrono::ceil is used but when compiling for earlier versions
a separate implementation is used to comply with C++11's limited
constexpr rules. Let's run the equivalent of the existing
std::chrono::ceil test cases on std::chrono::__detail::ceil too to make
sure that it doesn't get broken.

libstdc++-v3/ChangeLog:

	* testsuite/20_util/duration_cast/rounding_c++11.cc: Copy
	rounding.cc and alter to support compilation for C++11 and to
	test std::chrono::__detail::ceil.