useradd,userdel,usermod: Add -R/--root arg completion.
userdel: Add -h/--help non-completion.
luseradd,lusermod,luserdel: New completions.
man: Don't expand man page extensions too early.

Breaks for example subdir completions if there is a subdir whose name
matches extensions in the current dir.
ssh: Add some -o and related arg completions.
fix interface completion
add -p option completion
nc: New completion.
tar: Simplify bzip patterns.
tar: Recognize taz and tb2 as compressed tarballs.

http://en.wikipedia.org/wiki/Tar_(computing)#Naming_of_compressed_tar_files
ncftp: Add option completion.
Avoid sourcing dirs in completion loader to avoid fd leaks (RedHat: #903540).
Brown paper bag fix for the previous commit.
modprobe: Don't suggest installing already installed modules.
ngrep: New completion.
tshark: New completion.
_mac_addresses: Fix with net-tools' ifconfig that outputs ether, not HWaddr.
_mac_addresses: Try ARP cache with "ip neigh" if arp is not available.
wol: Try "ip addr" before ifconfig for finding out broadcast addresses.
_mac_addresses: Try local interfaces with "ip link" if ifconfig is N/A.