Added experimental Haiku OS support.

It compiles and it runs with some minor glitches.

src/network/network.c

@@ -351,6 +351,9 @@ int net_accept(int fd, struct ip_addr_encap* ipaddr)
 	{
 		switch (net_error())
 		{
+#if defined(__HAIKU__)
+			case ETIMEDOUT:
+#endif
 #if defined(__linux__)
 			case ENETDOWN:
 			case EPROTO:

src/system.h

@@ -81,7 +81,9 @@
 #include <pwd.h>
 #include <sys/resource.h>
 #define HAVE_STRNDUP
+#ifndef __HAIKU__
 #define HAVE_MEMMEM
+#endif
 #define HAVE_GETRLIMIT
 #endif