<sched.h>: Add sched_getcpu() and cpu_set_t

This adds the cpu_set_t type definition and related functions
and macros used to handle CPU thread affinity.

  sched_getcpu()
  sched_setaffinity()
  sched_getaffinity()

Change-Id: If382ecafde8926341a88478062b275553645065b
diff --git a/libc/docs/CHANGES.TXT b/libc/docs/CHANGES.TXT
index 67b9e76..8e23c0e 100644
--- a/libc/docs/CHANGES.TXT
+++ b/libc/docs/CHANGES.TXT
@@ -11,6 +11,9 @@
 
 - <time.h>: Add timegm(), timelocal(), time2posix() and posix2time()
 
+- <sched.h>: Add sched_getcpu(), sched_getaffinity(), sched_setaffinity(),
+  cpu_set_t and related macros (e.g. CPU_SETSIZE, CPU_ZERO, CPU_SET, ...)
+
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 Differences between Android 2.3 and Android 2.2: