Merge pull request #5064 from nicolasnoble/win32-python

include/grpc/impl/codegen/compression_types.h

include/grpc/impl/codegen/port_platform.h

include/grpc/impl/codegen/propagation_bits.h

setup.py

src/python/grpcio/grpc/_cython/.gitignore

src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi

src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi

src/python/grpcio/grpc/_cython/cygrpc.pyx

src/python/grpcio/grpc/_cython/imports.generated.c

src/python/grpcio/grpc/_cython/imports.generated.h

src/python/grpcio/grpc/_cython/loader.c

src/python/grpcio/grpc/_cython/loader.h

...c/python/grpcio/grpc/_cython/imports.generated.c.template

...c/python/grpcio/grpc/_cython/imports.generated.h.template