This adds the deprecated attribute to std::is_pod and std::is_pod_v for
C++20.

2019-12-05  JeanHeyd "ThePhD" Meneide  <phdofthehouse@gmail.com>

	* include/bits/c++config (_GLIBCXX20_DEPRECATED): Add new macro.
	* include/std/type_traits (is_pod, is_pod_v): Deprecate for C++20.
	* testuite/20_util/is_pod/deprecated-2a.cc: New test.

From-SVN: r280065