If -debug_dap flag is given, xsystem35 speaks the Debug Adapter Protocol
(https://microsoft.github.io/debug-adapter-protocol/) via stdin/stdout.
This enables xsystem35 to work as a backend of VS Code's Debugger (and
possibly other debuggers that support DAP).
If -debug option is specified, xsystem35 enables built-in debugger. It
optionally loads debug information from *SA.ALD.symbols file (generated
by xsys35c), and drops into a debugger REPL.
Currently the debugger supports:
- Simple breakpoints
- Backtrace
- Single-step execution (step into / step over)
- Printing variables
Also, when the debugger is enabled SIGINT breaks execution and enters a
REPL.