JDK 9 RFR of 8171452: (ch) linux io_util_md: Operation not supported exception after 8168628

[Brian Burkhalter]

Please review at your convenience:

Issue:	https://bugs.openjdk.java.net/browse/JDK-8171452
Patch:	http://cr.openjdk.java.net/~bpb/8171452/webrev.00/

Change on Linux to fall back to ftruncate64() if fallocate64() returns EOPNOTSUPP. I am wondering however whether the fall back should occur for *all* cases where ftruncate64() returns non-zero?

Thanks,

Brian