Merge pull request #267 from jemc/master

Problem: autogen.sh has no shebang
Problem: current shebang does not always work
Solution: change shebang to cross platform one

* Also changed comments on generated files to clarify their origin.

fixes zeromq/zyre#268
Merge pull request #270 from sappo/master

Problem: current shebang does not always work
Problem: Faulty zproject-generated code causes zyre problems in drops
Solution: Regenerate from corrected zproject