doc: go1.6.txt: text/template and space trimming

Change-Id: I33c0425361c98b175d8d87e0f7e44946bfb3e3fa
Reviewed-on: https://go-review.googlesource.com/14440Reviewed-by: Rob Pike <r@golang.org>

doc/go1.6.txt

@@ -10,3 +10,4 @@ API additions and behavior changes:
 
 strconv: QuoteToGraphic (https://golang.org/cl/14184/)
 text/template: ExecError (https://golang.org/cl/13957/)
+text/template: trimming spaces (https://golang.org/cl/14391/)