BUILD/SETUP.sh:
  BUG#25530 --with-readline fails with commercial source packages
  
  The compile-* scripts should not use --with-readline explicitly when no readline is present.
configure.in:
  BUG#25530 --with-readline fails with commercial source packages
  
  Configuring --with-readline should fail when libreadline is not bundled.
  A system libreadline is only used when there is a bundled libreadline too, so the commercial source code isn't linked with GPL libreadline by accident.