Don't check for HAVE_ defines in this header file, it is meant to be public

and we can't depend on configure-defines in it. This logic is borrowed from
the public curl headers.

ares/ares.h

@@ -20,7 +20,10 @@
 
 #include <sys/types.h>
 
-#ifdef HAVE_SYS_SELECT_H
+#ifdef _AIX
+/* HP-UX systems version 9, 10 and 11 lack sys/select.h and so does oldish
+   libc5-based Linux systems. Only include it on system that are known to
+   require it! */
 #include <sys/select.h>
 #endif