filtering of commands during async operation

[Andrew Cagney]

> The last time we did a tarball drop it meant that Adam ended up wasting time merging old ObjC code into the TOT gdb - work which we had already done on our branch.  It would be great not to do that again...

Adam has been quietly integrating/overhauling that very old objective-c 
code, and that work is still ongoing:
http://sources.redhat.com/ml/gdb-patches/2003-10/msg00581.html
What Adam did was definitly not a merge.

Andrew