libgo: update to autoconf 2.69 and automake 1.15.1

Initial patch from Joseph Myers.

Change-Id: I2c8e41f82ba27301ebf269e16cf64b7abb969d12
Reviewed-on: https://go-review.googlesource.com/c/146417
Reviewed-by: Ian Lance Taylor <iant@golang.org>
8 files changed