configure: Add missing <sys/socket.h> updates

Commit 7ebdf2cd62 ("scanadf: fixes for
various compilation warnings") missed these updates.

configure

@@ -4864,7 +4864,7 @@ fi
 
 
 
-for ac_header in os2.h fcntl.h unistd.h libc.h sys/time.h sys/types.h
+for ac_header in os2.h fcntl.h unistd.h libc.h sys/time.h sys/types.h sys/socket.h
 do
 as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
 if { as_var=$as_ac_Header; eval "test \"\${$as_var+set}\" = set"; }; then

include/sane/config.h.in

@@ -108,6 +108,9 @@
 /* Define to 1 if you have the `strtod' function. */
 #undef HAVE_STRTOD
 
+/* Define to 1 if you have the <sys/socket.h> header file. */
+#undef HAVE_SYS_SOCKET_H
+
 /* Define to 1 if you have the <sys/stat.h> header file. */
 #undef HAVE_SYS_STAT_H