Fix abs(long long) test in 32bit MSVC: need to calculate max value in Python as Cython assumes result to be Py_ssize_t (due to sizeof()), which is < sizeof(long long).

Configure another Cython option in test runner from *inside* the shard runner to support non-forking setups (i.e. Windows).

Configure Cython options in test runner from *inside* the shard runner to support non-forking setups (i.e. Windows).

More pypy3 fixes

Fixes a segfault on pypy3 due to the coroutine type missing tp_iternext in 5.8.

Last change accidentally disallowed mismatching 'nogil' assignments even when compatible. Reallow them, and clean up the last change a little.

Allow assignment of C function pointers with compatible exception declarations (not only exact matches).

Allow mismatches of broader exception declarations in .pxd signatures as long the implemented signature is covered.

Pass pyx_library kwargs to py_library

Previously, using "is_f_contig" and "is_c_contig" together would leave one of them undeclared.
Closes #1872.

Make vtable order of extension types with fused methods only dependant on the original declaration order (e.g. in the .pxd file).
Previously, fused methods were specialised and expanded on first use, which lead to an arbitrary order in the vtable.
Also fixes compile failures when inheriting from base types with fused cdef methods.
Fixes #1873.