If we have the XFS headers (at build time) we can use XFS specific ioctls
(once testing the file is on XFS) to better allocate space.

This dramatically improves performance of mysql-test-run cases as well:

e.g.
number of extents for ndb_dd_basic tablespaces and log files
BEFORE this patch: 57, 13, 212, 95, 17, 113 
WITH this patch  :  ALL 1 or 2 extents

(results are consistent over multiple runs. BEFORE always has several files
with lots of extents).

As for timing of test run:
BEFORE
ndb_dd_basic                   [ pass ]         107727
real    3m2.683s
user    0m1.360s
sys     0m1.192s

AFTER
ndb_dd_basic                   [ pass ]          70060
real    2m30.822s
user    0m1.220s
sys     0m1.404s

(results are again consistent over various runs)

similar for other tests (BEFORE and AFTER):
ndb_dd_alter                   [ pass ]         245360
ndb_dd_alter                   [ pass ]         211632