send can fail silently when sending would block (EWOULDBLOCK return for send) (#18)

* try to use a pipe for communication

* flush send buffer on the background thread

* cleanup

* linux fix / linux still use event fd for now

* cleanup

ixwebsocket/IXEventFd.h

@@ -6,6 +6,8 @@
 
 #pragma once
 
+#include <stdint.h>
+
 namespace ix
 {
     class EventFd {
@@ -13,11 +15,19 @@ namespace ix
         EventFd();
         virtual ~EventFd();
 
-        bool notify();
+        bool notify(uint64_t value);
         bool clear();
+        uint64_t read();
         int getFd();
 
     private:
+#if defined(__linux__)
         int _eventfd;
+#else
+        // Store file descriptors used by the communication pipe. Communication
+        // happens between a control thread and a background thread, which is
+        // blocked on select.
+        int _fildes[2];
+#endif
     };
 }