Improvements to vsFont rendering.

 * Fonts now remember their native size.
 * Fonts now only push a transform if they have a non-identity one to
   push.
 * Adds (disabled) a mode which doesn't vertically center text.  Need
   to think about this more.
 * Various fixes to vsFont to make it be able to draw pixel-perfect
   text.  Note that this requires drawing into a scene with an ortho
   projection which matches the number of pixels in the renderer.  (This
   doesn't work exactly right in HighDPI contexts, but it's probably
   close enough for government work).
 * Adds a new rendering command "SnapMatrix", which snaps the current
   local to world matrix to pixel coordinates, assuming the
   above-mentioned ortho matrix.  vsFonts now emit this command,
   when being built into a fragment.

Also:

 * Removed the remnants of compiling vsDisplayLists.  This has been
   disabled for ages (and is long-since deprecated in OpenGL code), but
   I'd never gotten around to fully removing the code.  Now it's
   gone.