doc/go1.7: mention CallersFrames and Frames

Change-Id: I73ae6a6837a6dcf75b3b8f431d97a18348e01a42
Reviewed-on: https://go-review.googlesource.com/19921Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.7.txt

@@ -10,6 +10,4 @@ SOMETHING WILL HAPPEN
 
 API additions and behavior changes:
 
-SOMETHING WILL HAPPEN
-
-
+runtime: add CallerFrames and Frames (CL 19869)