Squashed commit of the following:
Last minute clean-up
libs/libc/grp/lib_find_grpfile.c: Fix some problems found in testing.
libs/libc/pwd: Finishes off implementation using /etc/passwd.
libs/libc/grp: Finishes off implementation using /etc/group.
libs/libc/pwd/lib_find_pwdfile.c: Add logic to look up user information in /etc/passwd file, if available.
libs/libc/grp/lib_find_grpfile.c: Add logic to look up group information in /etc/group file, if available.
Gregory Nutt