The below patches implement MI -break-commands. As the name implies,
it's the same as CLI 'commands'. There are two patches: one
refactors CLI 'commands' for easier reuse, and the second actually
adds -break-commands. The patches mostly were derived from Apple
branch, and then adjusted for CVS HEAD. One functional change I've
made is that '-break-commands <number>' does not report the list
of currently set commands -- since -break-info already prints his
information, it does not seem necessary to add another way. I've
also added a test and docs.

The parts of this patch that are not MI are:
1. Slight refactoring of cli/cli-script.c
2. Slight refactoring of breakpoint.c

I'd appreciate if somebody could review them.

Eli, there's also doc change here, comments appreciated.

Thanks,
Volodya