[perl #31163] Debugger - List breakpoints

[Will Coleda]

To use the same debugger commands as perl (which I assume is a goal),  
we'd need to make this command "L".

The current implementation of the debugger is case agnostic as far as  
command names go, and since there's already an "l", there can't be an  
"L" as well.

Should we pick another name, or force commands to be case sensitive?