RFC: Fix breakpoint commands in MI

[Vladimir Prus]

Vladimir Prus wrote:

> 
> I've run into a couple of embarassing issues with breakpoint commands in MI:
> 
> 1. Complex commands, such as "while", are not parsed, and their content is
> treated as separate top-level commands.
> 
> 2. Breakpoint commands are not run at all.
> 
> The underlying issue there is that mi-break.exp actually does not verify that
> breakpoints are hit as desired, and while adding tests for -break-commands,
> I have blindly duplicated that issue.
> 
> This patch appears to do the right thing. Anybody has comments?

I've checked this in.

- Volodya