The V font is defined conditionally, so that it renders
like CB in output formats that support that, and like B
in those that don't (e.g. the terminal).
We could just redefine C, but this would affect code
blocks, too, and putting them all in boldface looks ugly,
I think.
Possible drawback: fragments created by pandoc's man
writer will presuppose a nonstandard V font.
Closes#7506.
Supersedes 253467a549.
c40727bfbb