Implement several enhancements to NUMA policies.

Add a new "interleave" allocation policy which stripes pages across
domains with a stride or width keeping contiguity within a multi-page
region.

Move the kernel to the dedicated numbered cpuset #2 making it possible
to assign kernel threads and memory policy separately from user.  This
also eliminates the need for the complicated interrupt binding code.

Add a sysctl API for viewing and manipulating domainsets.  Refactor some
of the cpuset_t manipulation code using the generic bitset type so that
it can be used for both.  This probably belongs in a dedicated subr file.

Attempt to improve the include situation.

Reviewed by:	kib
Discussed with:	jhb (cpuset parts)
Tested by:	pho (before review feedback)
Sponsored by:	Netflix, Dell/EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D14839

newlib/libc/sys/rtems/include/sys/_bitset.h

@@ -57,4 +57,10 @@ struct t {								\
  */
 #define BITSET_DEFINE_VAR(t)	BITSET_DEFINE(t, 1)
 
+/*
+ * Define a default type that can be used while manually specifying size
+ * to every call.
+ */
+BITSET_DEFINE(bitset, 1);
+
 #endif /* !_SYS__BITSET_H_ */