Convert some 8-cell mosaic glyphs into aliases to 6-cell

Convert some 8-cell mosaic glyphs into aliases to 6-cell

Because in Bedstead the cell boundaries of 8-cell mosaic glyphs are a
superset of those for 6-cell mosaic glyphs, each of the existing
6-cell glyphs has an identical 8-cell glyph whose middle two rows of
cells are identical.  Thus, these 8-cell glyphs can be aliases for the
corresponding 6-cell glyph.  I've implemented this as a macro called
A() that can be mixed in with the existing O() macros in the section
of the glyphs table that generates U+1CD00..U+1CDE5, aliasing them to
characters in U+1FB00..U+1FB3B.  That makes the table even more
confusing, but at least it's compact.