libgo: adapt runtime.inc to AIX

* Two AIX types are wrongfully exported to runtime.inc as their names
  make them look like a Go type.
* The sigset go type conflicts with a system sigset type.

Issue golang/go#19200

Change-Id: I235cb81e49c8f1e4d8e2396cd03b399572f02a61
Reviewed-on: https://go-review.googlesource.com/38192
Reviewed-by: Ian Lance Taylor <iant@golang.org>
1 file changed