FD_SETSIZE for internal polling defaults to 1024

If, when compiling 0MQ you don't set FD_SETSIZE,
it defaults to 1024 rather than to 64.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

src/select.cpp

@@ -23,6 +23,9 @@
 #include <algorithm>
 
 #ifdef ZMQ_HAVE_WINDOWS
+#if !defined FD_SETSIZE
+#define FD_SETSIZE 1024
+#endif
 #include "winsock2.h"
 #elif defined ZMQ_HAVE_HPUX
 #include <sys/param.h>