[Cython] C++ STL iteration bugs

[Stefan Behnel]

Hi,

I ran into a couple of problems with the new C++ STL integration, just
dumping them here for now.

Invalid C code when using a stack allocated C++ vector inside of a
generator, also lacking type conversion utility code:

https://github.com/cython/cython/commit/d0a8e24720c3ed4e723b5a1b204bf375780f51bd

Failure to compile iteration over pointer to C++ vector, apparently a type
inference bug:

https://github.com/cython/cython/commit/edd10c3b33afcac8f471ac6d6664e29f2d985d21

I may not be able to take a serious look at them within the next week but
would like to see them fixed for the release, so I'd be happy if someone
can manage to work on them.

Stefan