patch 8.1.0371: argument types for select() may be wrong

Problem:    Argument types for select() may be wrong.
Solution:   Use a configure macro. (Tobias Ulmer)
diff --git a/src/config.h.in b/src/config.h.in
index 00117cf..09420d2 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -113,6 +113,9 @@
 /* Define if you can safely include both <sys/time.h> and <sys/select.h>.  */
 #undef SYS_SELECT_WITH_SYS_TIME
 
+/* Define to a typecast for select() arguments 2, 3 and 4. */
+#undef SELECT_TYPE_ARG234
+
 /* Define if you have /dev/ptc */
 #undef HAVE_DEV_PTC