add api level 9 'since' flag to docs

Change-Id: Idee873a20ae0f3f0a9705997c8b73ce7f181906f
diff --git a/Android.mk b/Android.mk
index febd02d..c71d72e 100644
--- a/Android.mk
+++ b/Android.mk
@@ -375,6 +375,7 @@
     -since ./frameworks/base/api/6.xml 6 \
     -since ./frameworks/base/api/7.xml 7 \
     -since ./frameworks/base/api/8.xml 8 \
+    -since ./frameworks/base/api/9.xml 9 \
     -since ./frameworks/base/api/current.xml HC \
 		-werror -hide 113 \
 		-overview $(LOCAL_PATH)/core/java/overview.html