type inference can break 'del' statement

[scoder]

This fails to compile:

def test():
    x = 1    # inferred as int
    del x    # error: Deletion of non-Python, non-C++ object

[vitja]

fixed here  https://github.com/cython/cython/commit/0f122b6dfb6d0c7932b08cc35cdcc90c3c30257b