Set up rules to merge AndroidManifest.xmls

Now you can merge the library manifest files to the main app's
AndroidManifest.xml with LOCAL_FULL_LIBS_MANIFEST_FILES.
LOCAL_FULL_LIBS_MANIFEST_FILES is a list of paths relative to the top of
the source tree.

Bug: 12907528
Change-Id: I16a347c83dfb6fbbb7d5d40284b7c65aa682fdd2
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 8863fe6..7d7895c 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -109,6 +109,7 @@
 LOCAL_WARNINGS_ENABLE:=
 LOCAL_FULL_MANIFEST_FILE:=
 LOCAL_MANIFEST_FILE:=
+LOCAL_FULL_LIBS_MANIFEST_FILES:=
 LOCAL_RENDERSCRIPT_INCLUDES:=
 LOCAL_RENDERSCRIPT_INCLUDES_OVERRIDE:=
 LOCAL_RENDERSCRIPT_CC:=