Add back api= as an attribute to @RequiresApi

I changed the api= attribute to value= to make the
annotation more convenient to use, but apparently that
CL didn't make it into the beta1 build, so now that
code may be referencing api=, we'll need to include it
as well.

Change-Id: I5b267193923e28d4d45631c0715b460083fca828
diff --git a/annotations/src/android/support/annotation/RequiresApi.java b/annotations/src/android/support/annotation/RequiresApi.java
index 39f0b51..ddd3158 100644
--- a/annotations/src/android/support/annotation/RequiresApi.java
+++ b/annotations/src/android/support/annotation/RequiresApi.java
@@ -36,6 +36,14 @@
 @Retention(CLASS)
 @Target({TYPE,METHOD,CONSTRUCTOR,FIELD})
 public @interface RequiresApi {
+    /**
+     * The API level to require. Alias for {@link #api} which allows you to leave out the
+     * {@code api=} part.
+     */
     @IntRange(from=1)
-    int value();
+    int value() default 1;
+
+    /** The API level to require */
+    @IntRange(from=1)
+    int api() default 1;
 }