Add a simple work queue abstraction.

Makes it easy to schedule a bunch of work to happen in parallel.

Change-Id: Id9c0e52fc8b6d78d2b9ed4c2ee47abce0a01775c
diff --git a/libs/utils/Threads.cpp b/libs/utils/Threads.cpp
index ab207f5..f9277de 100644
--- a/libs/utils/Threads.cpp
+++ b/libs/utils/Threads.cpp
@@ -323,6 +323,7 @@
 #endif
 }
 
+#ifdef HAVE_ANDROID_OS
 int androidSetThreadSchedulingGroup(pid_t tid, int grp)
 {
     if (grp > ANDROID_TGROUP_MAX || grp < 0) { 
@@ -425,6 +426,7 @@
 
     return ret;
 }
+#endif
 
 namespace android {