libstdc++: Include <stdint.h> in <bits/atomic_wait.h>

This is needed in order to compile it as a header-unit, which might be
desired because it's included by both <atomic> and <semaphore>.

libstdc++-v3/ChangeLog:

	* include/bits/atomic_wait.h: Include <stdint.h>.

libstdc++-v3/include/bits/atomic_wait.h

@@ -35,6 +35,7 @@
 #include <bits/version.h>
 
 #if __glibcxx_atomic_wait
+#include <stdint.h>
 #include <bits/functional_hash.h>
 #include <bits/gthr.h>
 #include <ext/numeric_traits.h>