Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* include/bits/atomic_wait.h (_GLIBCXX_HAVE_PLATFORM_WAIT):
	Define before first attempt to check it.

Tested x86_64-linux and powerpc64-linux, not committed yet.

I think we need this, otherwise __platform_wait_uses_type<T> is false
for all T.