Replace groups.sh with groups.c.

* src/groups.c (main): New file, replacing groups.sh.
* src/group-list.c, src/group-list.h: New files, factored out of id.c,
implementing the functionality that "id" and "groups" have in common.
* src/id.c (print_full_info): Avoid a segfault when trying to print
an error message if getgroups fails.
(print_group_list): Move to group-list.c.
(print_group): Likewise.
* man/Makefile.am: When building groups.1, obtain the help text
from src/groups.c, not src/groups.sh.
(noinst_HEADERS): Add group-list.h.
(group): Remove rule.
(dist_man_MANS): Remove groups.1.
* doc/coreutils.texi (groups: Print group names a user is in):
Explain why "groups" and "groups $(id -un)" give different results
in existing login sessions after you change the group database.
(id: Print user identity): Likewise for "id".
* po/POTFILES.in: Add src/group-list.c and src/groups.c.
* NEWS: mention this.
* AUTHORS: Update.

1 files changed, 1 insertions, 1 deletions

diff --git a/AUTHORS b/AUTHORS
index 200e141d8..807857f9c 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -31,7 +31,7 @@ false: Jim Meyering
 fmt: Ross Paterson
 fold: David MacKenzie
 ginstall: David MacKenzie
-groups: David MacKenzie
+groups: David MacKenzie, James Youngman
 head: David MacKenzie, Jim Meyering
 hostid: Jim Meyering
 hostname: Jim Meyering