libbb: add xgetgrnam too. ~0 code size change

diff --git a/include/libbb.h b/include/libbb.h
index 80311db..16e8f48 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -703,6 +703,7 @@
 /* chown-like handling of "user[:[group]" */
 void parse_chown_usergroup_or_die(struct bb_uidgid_t *u, char *user_group) FAST_FUNC;
 struct passwd* xgetpwnam(const char *name) FAST_FUNC;
+struct group* xgetgrnam(const char *name) FAST_FUNC;
 struct passwd* xgetpwuid(uid_t uid) FAST_FUNC;
 struct group* xgetgrgid(gid_t gid) FAST_FUNC;
 char* xuid2uname(uid_t uid) FAST_FUNC;