Change group_lookup.l to re-read gid_map at runtime
Change group_lookup.l to re-read gid_map at runtime

Previously, the group_lookup.l lexer would only read the gid_map once
on the first call to glkup_gid_hosts and save the map in a static
variable.  Now, it frees the map on each call and reinitializes its
state from the gid_map on disk.

cmusatyalab/opendiamond,cmusatyalab/opendiamond,cmusatyalab/opendiamond,cmusatyalab/opendiamond,cmusatyalab/opendiamond