Improve the RetroShell debugger

[dirkwhoffmann]

RetroShell has a simple debugger which looks like this at the moment:

It provides elementary commands such as single stepping through the code.

I want to

• extend the debug capabilites AND
• do the same in VirtualC64 with a matching command syntax AND
• stick to some "standards" as much as possible

@mithrendal recommended to look at

• SMON (which was popular for the C64)
• Seka (which was popular for the Amiga)

Seka provides these symbolic debug commands:

TODO:

• Create a list of debugger commands that feals natural for both the Amiga and the C64.

[dirkwhoffmann]

For reference: Current debug commands

Command	Description
pause	Pauses emulation
continue	Continues emulation
step	Steps into the next instruction
next	Steps over the next instruction
goto	Redirects the program counter
disassemble	Runs the disassembler
break	Manages CPU breakpoints
watch	Manages CPU watchpoints
catch	Manages CPU catchpoints
cbreak	Manages Copper breakpoints
cwatch	Manages Copper watchpoints
os	AmigaOS debugger

[dirkwhoffmann]

Let's be bold and steal the following ideas from Seka:

1. Allow prefixes .b, .w, .l if it makes sense for the specific command.
2. Remember the last displayed address and use it as the default address for the next command:

3. Implement the ? operator which is pretty handy