OS X fsync isn't sufficient, use fcntl(F_FULLFSYNC) instead; note that
F_FULLFSYNC isn't supported on all OS X filesystems, fallback to fsync
if F_FULLFSYNC fails.
Merge pull request #1382 from wiredtiger/os-x-fullfsync

fix durability support on OS X
Sync the metadata before swapping the turtle file into place.

This was always the intention, and it used to happen, but a change move the fsync outside the checkpoint/schema lock (336dc23) left out the fsync of the metadata.

refs #1383.
Merge pull request #1384 from wiredtiger/metadata-sync

Sync the metadata before swapping the turtle file into place.