This patch adds a new substitution parameter only valid for the include 
parameter.

If %X is specified in an include parameter, then files named with the 
name of each group the user is a member of.
For example:

include = conf.%X

will search for and include the following files if they exist:

conf.wheel
conf.users
conf.sysadmin
conf.product

if the user is a member of those four groups, of course.