Haiku OS port (#485)

* Haiku OS port
* haiku with X11 backend
* haiku has stpncpy
* Haiku is not Linux.
* X not stable enough on Haiku
* Haiku : settimeofday is a no-op
* Haiku : no need to define settimeofday at all (pointed by nbriggs)

---------

Signed-off-by: Anarchos <sylvain_kerjean@hotmail.com>

src/unixfork.c

@@ -219,7 +219,9 @@ int fork_Unix(void) {
   /* interrupts need to be blocked here so subprocess won't see them */
   sigemptyset(&signals);
   sigaddset(&signals, SIGVTALRM);
+#ifndef MAIKO_OS_HAIKU
   sigaddset(&signals, SIGIO);
+#endif
   sigaddset(&signals, SIGALRM);
   sigaddset(&signals, SIGXFSZ);
   sigaddset(&signals, SIGFPE);