Why isn't bool allowed as AA key type?

[David Nadlinger]

Hello all,

is there a reason bool isn't allowed as key type for associative arrays 
(mtype.c:3995)? The docs don't mention this.

bool-key AAs probably wouldn't be too useful in practice, but it seems 
like a quite arbitrary and unexpected limitation to me – e.g. I would 
have to add special cases to all my Thrift map handling code.

In case this is not on purpose, I'd be happy to put together a pull request.

David