Only one polling mechanism is compiled

Till now wrappers for all the polling mechanisms available on
the given platform were compiled, although only one of them
was used. This patch compiles just the used one. This can
make libzmq binary more concise.

Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

src/devpoll.hpp

@@ -21,9 +21,9 @@
 #ifndef __ZMQ_DEVPOLL_HPP_INCLUDED__
 #define __ZMQ_DEVPOLL_HPP_INCLUDED__
 
-#include "platform.hpp"
-
-#if defined ZMQ_HAVE_SOLARIS || defined ZMQ_HAVE_HPUX
+//  poller.hpp decides which polling mechanism to use.
+#include "poller.hpp"
+#if defined ZMQ_USE_DEVPOLL
 
 #include <vector>
 
@@ -93,6 +93,8 @@ namespace zmq
         const devpoll_t &operator = (const devpoll_t&);
     };
 
+    typedef devpoll_t poller_t;
+
 }
 
 #endif