Log Message:
ascii: update to 3.18.

ChangeLog:

3.18: 2017-08-01
  Fix a packaging error, include NEWS in the tarball.

3.17: 2017-07-31
  Add -b option to generate a table with binary code-points.

3.16: 2017-07-18
  Add -a option to print in 4-column mode.
  0-fill fix and octal code-point literals.