Make the __bitcount*() functions unconditionally available, by moving

them out of the #if _BSD_VISIBLE block.  Other headers may depend on
__bitcount().  The dependencies can be a header not specified by
POSIX, and then namespace restrictions by _XOPEN_SOURCE are not
applicable, as it was reported.  Or, we might grow an implementation
of some POSIX facility using __bitcount(), which also should work.

Reported by:	Jason Schulz <schulz.j@gmail.com>
Discussed with:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

sys/sys/types.h

@@ -290,9 +290,6 @@ typedef	_Bool	bool;
  * The following are all things that really shouldn't exist in this header,
  * since its purpose is to provide typedefs, not miscellaneous doodads.
  */
-#if __BSD_VISIBLE
-
-#include <sys/select.h>
 
 #ifdef __POPCNT__
 #define	__bitcount64(x)	__builtin_popcountll((__uint64_t)(x))
@@ -356,6 +353,10 @@ __bitcount64(__uint64_t _x)
 #define	__bitcount(x)	__bitcount32((unsigned int)(x))
 #endif
 
+#if __BSD_VISIBLE
+
+#include <sys/select.h>
+
 /*
  * minor() gives a cookie instead of an index since we don't want to
  * change the meanings of bits 0-15 or waste time and space shifting