Update SDK Pkg revision for API 21 to 3 [DO NOT MERGE]

Added the do not merge tag so that it doesn't conflict with the version
number for the next API level.

Change-Id: Id9951894f845bdec2c6df9f923f9fbf67c9c2cfb

sdk/platform_source.prop_template

@@ -2,9 +2,9 @@ Pkg.Desc=Android SDK Platform ${PLATFORM_VERSION}
 Pkg.UserSrc=false
 Platform.Version=${PLATFORM_VERSION}
 Platform.CodeName=LOLLIPOP
-Pkg.Revision=2
+Pkg.Revision=3
 AndroidVersion.ApiLevel=${PLATFORM_SDK_VERSION}
 AndroidVersion.CodeName=${PLATFORM_VERSION_CODENAME}
-Layoutlib.Api=12
-Layoutlib.Revision=2
+Layoutlib.Api=13
+Layoutlib.Revision=3
 Platform.MinToolsRev=22