Add a new simple object "brei_result" that maps to the protocol-type
reason + explanation. That object is now returned instead of the errno,
giving us better debugging options.
This changes the dispatcher functions from returning an int to returning
a brei_result instead (default NULL for success). A helper function for
converting a neg errno to a result is provided for convenience for now,
eventually all these paths should deal with things correctly.
This is effectively the same as connection.sync, but goes the other way.
This adds the ei_callback.done request.
In libeis this is (currently) enforced immediately after sending the
connection object. Not required there and makes the code a bit messier
but this way we can ensure that any client library handles that part of
the code.
Directly copied from wayland. Note that while the wayland protocol
specifies the data is the last event serial in our case here it's just
0 since we don't have any event serials (yet).
The sync request is currently triggered after connection, merely to
ensure it works, it's not actually needed.
