libc: add clock ids CLOCK_REALTIME_ALARM and CLOCK_BOOTTIME_ALARM

(cherry-pick of b928bda83d4413b703329f607e2706602f15293f.)

Change-Id: Ica6aad84299819ffc5e57ae4891e057d2e401fa1
diff --git a/libc/include/time.h b/libc/include/time.h
index e280e0a..edcc5bd 100644
--- a/libc/include/time.h
+++ b/libc/include/time.h
@@ -104,6 +104,8 @@
 #define CLOCK_REALTIME_HR          4
 #define CLOCK_MONOTONIC_HR         5
 #define CLOCK_BOOTTIME             7
+#define CLOCK_REALTIME_ALARM       8
+#define CLOCK_BOOTTIME_ALARM       9
 
 extern int  timer_create(int, struct sigevent*, timer_t*);
 extern int  timer_delete(timer_t);