multi-column markup function/macro?

[Kieren MacMillan]

Hello all,

Before I reinvent the wheel… does anyone have a good multi-column markup 
function?

Must Haves:
1. Takes a markup-list and breaks it into n columns, with n=2 and n=3.
2. Accepts line-width override.

Nice To Haves:
1. n>3 columns
2. Works nicely with Lily’s built-in page-breaking algorithm (i.e., will break 
1 long markup-list into multiple pages of multiple columns).
3. Independent column controls (width, gutter, etc.).

Thanks!
Kieren.