translating Cocoa's obj'c to Ada's concurrency

1.24: adda/co/translating Cocoa's obj'c to Ada's concurrency:
. Hillegass's mac book has an inspiring section on concurrency .
summary:
the key to no race conditions is no indirect use of
shared modified variables;
anything done with the Cocoa libraries
should get exec'd as a msg sent to the main thread .

. adda needs a way to know when a function is
calling something that is not thread safe,
ie, not only can it not be allowed to modify non-locals,
it can't even call anyting that would modify a non-local
-- or even read a non-local if there's a chance that
some other thread might modify it .
. or else,
it can put mutexes around code doing the reading;
or, it can put shared globals in ada's protected var,
getting all requests by queue
and putting all outputs on a temp pointer provided by caller:
eg, "( this is one of the pointers on my mailbox,
it will be reserved for your response;
I will check it for non-nil until I find something ).