Log Message:
devel/smake: Update to 1.6nb1

- smake: Fixed a typo in a comment in readfile.c

- smake: The man page now mentions that the commands called for
  .INCLUDE_FAILED: should include $^ as argument to the rule command to
  be able to know what filename is missing and to be pocessed.

- smake: Fix a bug in the man page for .INCLUDE_FAILED:. It now
  correctly mentions that .INCLUDE_FAILED: only applies to the "include"
  directive but not to the "-include" directive as well (as claimed
  before).