Remove ENABLE_DRAFTS option

[stephanlachnit]

This option added ZMQ_BUILD_DRAFT_API to the compile definitions. However, this should be propagated by libzmq (see https://github.com/zeromq/libzmq/pull/4323 and https://github.com/zeromq/cppzmq/issues/477).

Closes https://github.com/zeromq/cppzmq/issues/477.

[coveralls]

I am not sure if I understand the problem here completely. Shutting down monitoring right is rather tricky, unfortunately. I am currently investigating an issue in libzmq related to that as well. Could you share a test case that demonstrates the problem?

[gummif]

This change will probably break something for someone using slightly older versions of libzmq.

[stephanlachnit]

This change will probably break something for someone using slightly older versions of libzmq.

Yes, I would recommend merging this change only after a new release of libzmq (the commit in question is not part of a release yet), since it is fairly reasonable to expect people not to take a new version of cppzmq and an old version libzmq.

[stephanlachnit]

@gummif since libzmq v4.3.5 has been released with https://github.com/zeromq/libzmq/issues/4194 included, this can merged now

[stephanlachnit]

I also updated the CI to use 4.3.5. to actually use this change.

[gummif]

Sorry for the delay. I will see if I have time soon to do a review.

[stephanlachnit]

@gummif friendly ping to check this :) This is quite a small change