Fixup BSD specific things from last merge

There's entries for header files we don't use, and the cvsimport doesn't
like removing files automatically, etc., and it won't have known to have
done this from autoconf's POV, so define that in the correct place, hence
the removal of the previously committed Makefile.

cmd-show-messages.c

@@ -21,7 +21,6 @@
 #include <string.h>
 #include <time.h>
 #include <unistd.h>
-#include <vis.h>
 
 #include "tmux.h"