libgo: regenerate config.h.in, add direntType unused attribute

These were accidentally left out of the update to 1.16beta1.

Change-Id: I80160d8e54f403efa05dcc4ccd950f641a8fd542
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/280872
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
2 files changed