Fix nasty bug where make(1) assumed that you could read the directory it

was in.  This shall be MFC'd in about three days (probably not a good idea
to MFC the stylistic changes though - see below).

PR:		19978
Submitted by:	Gerald Pfeifer <pfeifer@dbai.tuwien.ac.at>
Patch by:	roam (slightly modified by me to use NULL not NIL)

usr.bin/make/dir.c

@@ -223,6 +223,8 @@ Dir_Init ()
      */
     Dir_AddDir (openDirectories, ".");
     dot = (Path *) Lst_DeQueue (openDirectories);
+    if (dot == (Path *) NULL)
+	err(1, "cannot open current directory");
 
     /*
      * We always need to have dot around, so we increment its reference count