doc/go1.5.txt: huge integers are parse errors in text/template

Change-Id: Ie9331d102224290833c96a1535cdb96102a7fe9e
Reviewed-on: https://go-review.googlesource.com/9633Reviewed-by: Rob Pike <r@golang.org>

doc/go1.5.txt

@@ -64,6 +64,7 @@ syscall: Add Foreground and Pgid to SysProcAttr (https://golang.org/cl/5130)
 syscall: add missing Syscall9 for darwin/amd64 (https://golang.org/cl/6555)
 testing/quick: support generation of arrays (https://golang.org/cl/3865)
 text/template: add Options method (https://golang.org/cl/8462)
+text/template: huge integers are now parse errors (https://golang.org/cl/9651)
 time: add time.AppendFormat(https://golang.org/cl/1760)
 
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