Made the setting of the O_DIRECT flag be done in a later fcntl call, made crashing be replaced with a warning to the user.
Moved create_account and destroy_account methods to disk.cc.
Merge branch 'next' into sam_47
Merge branch 'sam_nofsck' into sam_47
Made the linux_file_t construction API be such that non-open objects are inconstructible by API.  Also removed the method exists() which would have always returned true and was brokenly implemented anyway.
Removed the unused exists() method from mock_file_t.
Removed unused serializer function check_existing.
Made the interface for constructing a linux_file_t be put outside the constructor, made it actually return the FILE_OPEN_BUFFERED return code.  The serializer logs the warning about the buffer cache.
Made open_direct_file actually be capable of returning an error result, pushing the crash out to the serializer.
Merge branch 'next' into sam_47
Changed direct I/O warning message to reference "performance problems".
Added O_DSYNC to flags (on Linux).
Made us use F_FULLSYNC (on OS X) in the pool-based diskmgr -- but have not tested this code on OS X.
Fixed compilation problems with F_FULLFSYNC symbol in pool.cc (on OS X).
Merge branch 'next' into sam_47
Merge branch 'next' into sam_47
Added comment about F_FULLFSYNC call.
Merge branch 'next' into sam_47
Changed the comment about O_LARGEFILE.
Added comment about the suddenly-confusing O_NOATIME flag.