Pull in an OrangeFS branch containing miscellaneous improvements.

- clean up debugfs globals
- remove dead code in sysfs
- reorganize duplicated sysfs attribute structs
- consolidate sysfs show and store functions
- remove duplicated sysfs_ops structures
- describe organization of sysfs
- make devreq_mutex static
- g_orangefs_stats -> orangefs_stats for consistency
- rename most remaining global variables