MI: type prefixes for values

[Eli Zaretskii]

> Date: Fri, 17 Feb 2006 14:35:56 -0500
> From: Daniel Jacobowitz <drow@false.org>
> Cc: Vladimir Prus <ghost@cs.msu.su>, gdb@sources.redhat.com
> 
> Writing a grammar for it would be difficult-to-impractical.

It doesn't need to be a formal grammar, just a spec that is accurate
enough to build a reader.

MI should have a regular syntax which allows such a spec.  If MI
doesn't support that, then it misses its main design goal.