libutils: add a binary blob cache implementation.

This change adds an implementation of a cache that stores key/value
pairs of unstructured binary blobs.

Change-Id: Idd01fdabedfa3aed6d359a6efb0592967af52651
diff --git a/libs/utils/tests/Android.mk b/libs/utils/tests/Android.mk
index 72d4876..87ad98e 100644
--- a/libs/utils/tests/Android.mk
+++ b/libs/utils/tests/Android.mk
@@ -6,6 +6,7 @@
 
 # Build the unit tests.
 test_src_files := \
+	BlobCache_test.cpp \
 	ObbFile_test.cpp \
 	Looper_test.cpp \
 	String8_test.cpp \