Multi-line aliases, runtypes, loadtypes etc

[stevesims]

In MOS 3 we have support for aliases, but currently they are restricted to performing a single command

RISC OS systems would support multiple commands within a single alias. commands would be split using |M (ctrl-M, a carriage-return character).

We should support this too. This applies to command aliases, runtypes, and loadtypes too.

(Hotkey definitions should ideally support this as well, however that likely requires a completely different approach to be taken for how hotkeys are handled in the line editor.)

[stevesims]

Multi-line handling of hotkeys is likely strongly related to #18 and/or #8