patch 8.2.0320: no Haiku support

Problem:    No Haiku support.
Solution:   Add support for Haiku. (Emir Sari, closes #5605)
diff --git a/src/term.c b/src/term.c
index e9a9004..6afecba 100644
--- a/src/term.c
+++ b/src/term.c
@@ -1420,6 +1420,11 @@
 # define DEFAULT_TERM	(char_u *)"beos-ansi"
 #endif
 
+#ifdef __HAIKU__
+# undef DEFAULT_TERM
+# define DEFAULT_TERM	(char_u *)"xterm"
+#endif
+
 #ifndef DEFAULT_TERM
 # define DEFAULT_TERM	(char_u *)"dumb"
 #endif