Support for multi-line errors

[liquidev]

Nim sometimes outputs errors that span multiple lines, eg. type mismatches. Example:

/home/daknus/Coding/Nim/tsuki/src/tsuki/vm.nim(271, 4) Error: type mismatch: got <State>
but expected one of:
proc interpret(s: State; chunk: Chunk; procName = "<main chunk>";
               initialStack: seq[Value] = @[])
  first type mismatch at position: 2
  missing parameter: chunk

expression: interpret(s)

The default interpreter shouldn't have to support this

This could be implemented as maybe a keyboard shortcut to show the whole error in an autocomplete-like popup, appearing below the error message.