Option parsing with flag package.
VIA dump options: -via-dump-binary, -via-dump-ascii.
Logging option: -log-file=... (default /dev/null)
Shortened var options => opt.
.gitignore entries imported from github/gitignore repo.
Imported github.com/peterh/liner lib.
Beginnings of a basic debugger / monitor.
Debugger input handling slightly more robust. Exit command.
Debugger has `run` command.
Debugger input handling work; DebuggerCommand struct etc.
CPU reads instruction+operand before incrementing PC.

This allows for a debugger to intercept the instruction before it
executes, while seeing the clean state of the PC before the instruction
was loaded.
Debugger receives the Iop object.
Debugger supports break-instruction (bi) command.

Sets a (single) breakpoint for the given instruction mnemonic.
e.g. break-instruction NOP
Debugger can set breakpoints against register values.

Examples:

    * break-register x 0xAE
    * br A 174
    * run
Debugger can set breakpoint for PC address.

Examples:

  * break-address 0xE0C7
  * break-addr 0x0123
  * ba 0xE1C0
Debugger show upcoming instruction.
Debugger treats "q" as "quit".
Debugger commands are case-insensitive (auto-lower-cased).
Debugger has help command.