🚀 go-pugleaf

There is a similar problem with eqn.
To include an expression of a determinant,
we write

	left | matrix { ... } right |

and this causes the same problem on LaserWriter,
although another implementation using the fonts
contained in Documentor's Workbench prints out very nicely.

In this case, the problem arose from the fact that eqn
translates vertical line specification into multiple "|"s,
and I wondered whether to rearrange the font itself.
But I finally decided to add new specifications to eqn:

	{left|right} {v|V}

where "v" yields \(br and "V" does \(bv.