Improvements to SAA5051 and SAA5052 characters

Improvements to SAA5051 and SAA5052 characters

In addition to their obviously distinctive national characters, the
SAA5051 and SAA5052 also change the shape of some standard characters
compared to the SAA5050.  I had spotted some of these, but noticed
several more when using an actual SAA5051 in my Acorn System 3.  The
unusual characters are apparently much easier to spot on screen than
in a datasheet.

Now, I think, we actually have the correct characters for each of
these chips.  In many cases, they're the same as one another, and in
those cases I've aliased the glyphs.