doc/progs: disable cgo tests that use C.Stdout on Solaris

doc/progs: disable cgo tests that use C.Stdout on Solaris

Solaris, like Windows, NetBSD and OpenBSD, uses macros for stdin, stdout,
and stderr. Cgo can't access them without getters/setters written in
C. Because of this we disable affected tests like for the other platforms.

Updates #10715.

Change-Id: I3d33a5554b5ba209273dbdff992925a38a281b42
Reviewed-on: https://go-review.googlesource.com/8264
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>