AIX wants sys/select.h

include/curl/multi.h

@@ -49,6 +49,7 @@
 #if defined(WIN32) && !defined(__GNUC__) || defined(__MINGW32__)
 #include <winsock.h>
 #else
+#include <sys/select.h>
 #include <sys/socket.h>
 #include <sys/time.h>
 #include <sys/types.h>