clear_breakpoint cleanup

[Jim Blandy]

Vladimir Prus <vladimir at codesourcery.com> writes:
> Now, clear_breakpoint directly removes breakpoints from
> global breakpoint list, even though delete_breakpoint
> can do it just fine. This is not causing any bugs, but
> for code simplicity sake, I'd like to reduce the amount
> of code that accesses breakpoint list. The following
> patch causes no regressions. OK?

This looks good to me.