[cli-users] Use comma instead of vertical bar to separate flag names in documentation

[Leo Gaskin]

Hello Boris!

I have been using your CLI description language to implement a
small command line tool. Working with the language, especially in
conjunction with your build2 build system has so far been an
absolute pleasure, as far as C++ is concerned.

However, one thing I have noticed is that, when specifying
multiple alternate flag names, e.g `--verbose` and `-v` the CLI
compiler separates them with the vertical bar `|` in generated
documentation.

It seems customary to instead use a comma and space to separate
them. (See `man 1 make`, `man 1 git`, ...). Some tools that parse
manual pages also rely on this convention.

Do you have a strong preference for the vertical bar, or would
you be willing use the more common comma style?

Many thanks
Leo Gaskin