[cairo] rescaled fonts test

[Adrian Johnson]

Jeff Muizelaar wrote:
> The attached adds a test case that uses user fonts to draw a monospaced
> font with the metrics of Bitstream Vera Sans.
> 
> The ability to draw glyphs with different metrics is useful when doing
> font substitution with fixed layout like in pdf and I eventually plan on
> adding code to poppler to do something similar.
> 
> This test case also exposes a bug in the pdf backend: the glyphs do not
> appear rescaled.

Should be fixed now.

I recommend using opaque colors in your test otherwise the PS output 
will only contain fallback images.