Inconsistent point types between terminals

Hi. I just stumbled upon another bug-looking behavior.

The different point types aren't the same across terminals. There's no
specific reason for that, right?

I do this:

  set terminal x11
  test

Note that point type 18 is a solid square

Then I do this:

  set terminal qt
  test

A solid square is now type 20. pdf works like qt, it looks like; I
haven't tested any others. I have no cycles to fix it right now, but can
put it on my list.

dima