Add a copy of api-versions.xml in prebuilts DO NOT MERGE

This CL adds a copy of api-versions.xml from the last release of
platform tools (25.0.3). This file will be included in a few more
releases of the platform tools, but will eventually be moved to
either be part of Studio or of the platform itself.

Test: N/A
Change-Id: Ibcd85249003552b52544997782c68fc5cb784b3e
diff --git a/sdk-annotations/README.txt b/sdk-annotations/README.txt
index c4342b6..da6a1e0 100644
--- a/sdk-annotations/README.txt
+++ b/sdk-annotations/README.txt
@@ -1,6 +1,13 @@
-Generated from tools/adt/idea CL
+annotations.zip was generated from tools/adt/idea CL
 234839667c6912ff7eaccd9102525d0ba495c886
 
 (by building the Android Studio tree by running ./build_studio.sh
 in tools/idea, then copying the resulting androidAnnotations.jar
 as this annotations.zip file.)
+
+----
+
+api-versions.xml was copied from platform-tools version 25.0.3.
+This file is typically generated as part of the SDK build process,
+but the AOSP build doesn't have the correct bits so this is a
+prebuilt from the last release.