[7u10] Request for approval: 7191556 (fs) UnixNativeDispatcher.getextmntent should be moved into platform specific code

[Seán Coffey]

I'd like to backport this changeset to the jdk7u release. Changeset 
applies without issue.
Build & tests successful.

bug report : http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7191556
jdk 8 changeset : http://hg.openjdk.java.net/jdk8/tl/jdk/rev/e48a9a1c14e3
jdk8 review thread : 
http://mail.openjdk.java.net/pipermail/nio-dev/2012-August/001824.html

regards,
Sean.