patch 8.2.0320: no Haiku support

Problem:    No Haiku support.
Solution:   Add support for Haiku. (Emir Sari, closes #5605)
diff --git a/src/pty.c b/src/pty.c
index a44d0a0..03c02af 100644
--- a/src/pty.c
+++ b/src/pty.c
@@ -386,7 +386,7 @@
 static char PtyProto[] = "/dev/ptym/ptyXY";
 static char TtyProto[] = "/dev/pty/ttyXY";
 # else
-#  ifdef __BEOS__
+#  if defined (__BEOS__) || defined(__HAIKU__)
 static char PtyProto[] = "/dev/pt/XY";
 static char TtyProto[] = "/dev/tt/XY";
 #  else