Write "generated by Cython" header also in .h files

exclude two more modules from stdlib compilation that require bootstrapping before importing Cython modules

Fix the placement of a closing bracket

avoid antipattern of sum()-ing lists

clean up decoding error reporting by counting lines instead of reading single characters to find the error position

disable asyncio coroutine test in Py3.4(.3) due to an annoying type check: Py3.5 has a fix and later 3.4 versions might, too

Revert "make Coroutine type a non-iterable/iterator and instead let __await__() return a thin Iterator wrapper"

This reverts commit cf51fa4e.