Add checking for id_t, and changed some of the type checking to use

the newer, recommended method.  (Couldn't switch uid_t and gid_t.)

configure.in

@@ -353,10 +353,7 @@ AC_C_LONG_DOUBLE
 
 AC_TYPE_SIGNAL
 AC_TYPE_UID_T
-AC_TYPE_MODE_T
-AC_TYPE_OFF_T
-AC_TYPE_SIZE_T
-AC_TYPE_PID_T
+AC_CHECK_TYPES([mode_t,off_t,size_t,pid_t,id_t])
 AC_TYPE_GETGROUPS
 AC_CHECK_MEMBERS([struct stat.st_rdev])