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/Android.mk b/libs/utils/Android.mk
index 87d0fb2..b4fc994 100644
--- a/libs/utils/Android.mk
+++ b/libs/utils/Android.mk
@@ -41,6 +41,7 @@
 	Tokenizer.cpp \
 	Unicode.cpp \
 	VectorImpl.cpp \
+	WorkQueue.cpp \
 	misc.cpp
 
 host_commonCflags := -DLIBUTILS_NATIVE=1 $(TOOL_CFLAGS)