add cpu affinity interfaces

this first commit just includes the CPU_* and sched_* interfaces, not
the pthread_* interfaces, which may be added later. simple
sanity-check testing has been done for the basic interfaces, but most
of the macros have not yet been tested.

src/sched/sched_cpucount.c

@@ -0,0 +1,11 @@
+#define _GNU_SOURCE
+#include <sched.h>
+
+int __sched_cpucount(size_t size, const cpu_set_t *set)
+{
+	size_t i, j, cnt=0;
+	const unsigned char *p = (const void *)set;
+	for (i=0; i<size; i++) for (j=0; j<8; j++)
+		if (p[i] & (1<<j)) cnt++;
+	return cnt;
+}

src/sched/sched_getaffinity.c

@@ -0,0 +1,10 @@
+#define _GNU_SOURCE
+#include <sched.h>
+#include "syscall.h"
+
+int sched_getaffinity(pid_t tid, size_t size, cpu_set_t *set)
+{
+	long ret = __syscall(SYS_sched_getaffinity, tid, size, set);
+	if (ret > 0) ret = 0;
+	return __syscall_ret(ret);
+}

src/sched/sched_setaffinity.c

@@ -0,0 +1,8 @@
+#define _GNU_SOURCE
+#include <sched.h>
+#include "syscall.h"
+
+int sched_setaffinity(pid_t tid, size_t size, const cpu_set_t *set)
+{
+	return syscall(SYS_sched_setaffinity, tid, size, set);
+}