Detect load address in PRG-files and ask to do a SYS to load address

Example:

*PRG-file with load address `0xC000`:*
```
0x00,0xC0,0xA9,0x0E,0x20,0xD2,0xFF,0xA9,...
```

When loading the file:

*Message box (or hotkey?):*
> Would you like to run `SYS49152`?
