lib/gshadow_.h: Fix compatibility with libc's struct sgrp

lib/gshadow_.h: Fix compatibility with libc's struct sgrp

The name of the first field was different.  Rename for compatiblity with
libc.

	$ diff -wU10 \
		<(grepc sgrp . | sed_rm_ccomments) \
		<(grepc sgrp /usr/include/ | sed_rm_ccomments);
	--- /dev/fd/63	2024-11-06 14:49:03.287204461 +0100
	+++ /dev/fd/62	2024-11-06 14:49:03.287204461 +0100
	@@ -1,6 +1,7 @@
	-./lib/gshadow_.h:struct sgrp {
	-	char *sg_name;
	+/usr/include/gshadow.h:struct sgrp
	+  {
	+    char *sg_namp;
		char *sg_passwd;
		char **sg_adm;
		char **sg_mem;
	 };

This originates from a typo in this project, which was later copied by
glibc, and so the typo was set in stone.  The typo was eventually fixed
in shadow, but glibc had already set the name in stone, so we should
just learn to live with it.

	$ grep -rn -C3 sg_name ChangeLog
	1607-
	1608-2011-07-30  Nicolas François  <nicolas.francois@centraliens.net>
	1609-
	1610:	* src/chgpasswd.c: Fix typo sp -> sg. sg_namp -> sg_name
	1611-	* src/chgpasswd.c: Always update the group file when SHADOWGRP is
	1612-	not enabled.
	1613-

This is a scripted change:

	$ find lib* src -type f \
	| xargs sed -i 's/\<sg_name\>/sg_namp/g';

Reviewed-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>