Tidy up mav_ip_subnet_cmp() and match_unix_group()
Tidy up mav_ip_subnet_cmp() and match_unix_group()

Fixes a harmless warning about possible use of uninitialised data in
match_unix_group (on GCC 4.0.3, disappears by GCC 4.3.1).

Improves an ENOMEM error message, removes an unnecessary memset(0),
localises the "mask" variable and renames "count" to "addrlen".

dell-oss/mod_auth_vas,dell-oss/mod_auth_vas