Glk zero-size windows; character input in graphics windows

Following this thread:

…I have added some text to the Glk update proposal page: … ec-changes

Short form:

  • Resizing a window to zero-size is called out as okay, with the caveat that you might not get input events from it while it’s hidden this way.
  • Requesting character input from a graphics window is now legal. But you have to do a gestalt test first, because interpreters may not support it (and older interpreters certainly won’t).