[DO NOT MERGE] librdkafka static bundle fixes required for next release

[edenhill]

THIS MUST NOT BE MERGED BEFORE THE NEXT IMPORT

So what you do is, when it is time for the next librdkafka import or RC:
$ git checkout master
$ git pull --rebase origin master
$ git fetch --tags
$ git checkout impfix # this PR
$ cd kafka/librdkafka_vendor
$ ./import.sh --develop /tmp/librdkafka-static-bundle-v2.0.0-RC2.tgz # or whatever version

If everything is ok, push it:

$ git checkout import_v2.0.0-RC2 # or whatever verison it is
$ push --dry-run origin import_v2.0.0-RC2

Go to github, review, MERGE! Do not squash or rebase, MERGE!

[emasab]

This was included, initially accidentally with RC4 in a squash-merge while migrating to SemaphoreCI, the second time with 2.0.0 the static bundle was merged correctly with a merge commit.