Change XQTR_S and YQTR_S to 29

Change XQTR_S and YQTR_S to 29

The consequence of this is to narrow the diagonal strokes.  They go
from being 6% wider than horizontal and vertical strokes to being 0.4%
wider.  I like the consistency, but it also has a practical advantage:
at round pixel sizes the daigonal edges no longer pass through pixel
centres.  This means that we're no longer at the mercy of rasterizer
tie-breaking rules so (for instance) Ghostscripts rasterizations are
symmetric now.

Since the shape of diagonal lines on a real SAA5050 is determined by
both edges of a clock whose duty cycle is only specified as being
between 0.4 and 0.6, I claim this is still within the tolerances of
the original.