Bugs fixed:
- String forward references to extension types like @cython.locals(x="ExtType") failed to find the named type. (Github issue #1962)
- NumPy slicing generated incorrect results when compiled with Pythran. Original patch by Serge Guelton (Github issue #1946).
- Fix "undefined reference" linker error for generators on Windows in Py3.3-3.5. (Github issue #1968)
- Adapt to recent C-API change of PyThreadState in CPython 3.7.
- Fix signature of PyWeakref_GetObject() API declaration. Patch by Jeroen Demeyer (Github issue #1975).