[Devel] smooth rasterizer fix

[David Turner]

Hello,

  I have just commited a several fixes to the smooth rasterizer.
  Mainly:

    - "setjmp/longjmp" is now used to handle raster pool overflow
      (instead of testing function calls). Funnily, this tends to
      make the rasterizer slightly faster..

    - functions have been renamed, and are now all prefixed with
      "gray_"

    - a new type (TArea) has been defined to hold the value of
      cell areas. It seems that using "int" wasn't enough on 16-bit
      systems since (2*PIXEL_BITS+2 == 18 bits) were needed, so the
      new code check for "UINT_MAX" to define TArea..

  I believe that this could solve the 16-vit problem that Wolfgang
  recently discovered, and I'd like his input if possible since I
  don't have the time to test this here..

  I don't think this will fix the "extremely thin lines" rendering
  bug, but who knows ?? (something I need to check too..)


Cheers,

- David