It does not seem that MI spec ever mentions escape sequence support
(where it's supported) or lack of such support. This patch tries to
fix that. 

Note that parse_escape function supports more than C language escape
sequences, it seems, but given that the function has no comments on
those sequences, and given that manual does not say anything about
that either, I don't feel like reverse-engineering the code to
document the exact rules. "As in C" as sufficient, I think, for MI
manual.

OK?

- Volodya