Add statement about source code availability for Prolog Cafe

EPL ยง3 states:

  A Contributor [i.e.: Gerrit Code Review] may choose to distribute
  the Program in object code form under its own license agreement,
  provided that:
  [...]
  b) its license agreement:
  [...]
  iv) states that source code for the Program [i.e.: Prolog Cafe] is
  available from such Contributor, and informs licensees how to obtain
  it in a reasonable manner on or through a medium customarily used
  for software exchange.

Change-Id: Ie002e0baf560fe219838e3bd49d5a103a75f44db
1 file changed