bug#24531: process-send-string seems to truncate lines over 4096 characters

[Stefan Monnier]

> I see that this bug is about 13 years old.  I think there's a pretty
> obvious solution: process-connection-type should default to nil.

In practice, that can't fly because it'll break existing code.

Also I don't think either value of `process-connection-type` is a good
option.  IOW, I think that the connection type should be a mandatory
argument when creating an async process (except maybe for those
processes with no input/output).

So maybe, the default value of `process-connection-type` should be
`unspecified` and the process creation code should emit a warning when
creating a process whose connection type is `unspecified` (just
a warning, tho: it should then pursue execution as if that value was t,
as usual, so as to preserve compatibility).


        Stefan