Fix compile errors on OpenBSD

- <pthread.h> included for the "pthread_t" type definition.
- <net/ethernet.h> include removed as the header doesn't exist.
- AI_ALL and AI_V4MAPPED defined to 0 as the options don't exist.

src/Mayaqua/Network.h

@@ -13,6 +13,10 @@
 
 #ifdef OS_UNIX
 #include <netinet/in.h>
+
+#ifdef UNIX_OPENBSD
+#include <pthread.h>
+#endif
 #endif
 
 // Dynamic Value