unix: extend rlimit test on Linux
unix: extend rlimit test on Linux

The basic Getrlimit functionality is already tested in TestRlimit. Use
the Linux-specific test to check whether setting RLIMIT_AS has the
desired effect regarding mmap, as specified in
http://man7.org/linux/man-pages/man2/getrlimit.2.html

Change-Id: I3e2c5769d9144cb4059735709a89a12f42568465
Reviewed-on: https://go-review.googlesource.com/100175
Run-TryBot: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

multiplay/golang-sys,multiplay/golang-sys,golang/sys,multiplay/golang-sys,multiplay/golang-sys,golang/sys,golang/sys