Change the cvode wrapper to reflect changes made in Cython > 28 whereby files 'source.pxd' are not automatically included in the 'source.pyx' file

Author: rpep

fidimag/common/sundials/cvode.pyx

@@ -6,6 +6,8 @@ np.import_array()  # don't remove or you'll segfault
 from libc.string cimport memcpy
 import sys
 
+from cvodedecs cimport *
+
 cdef extern from "../../atomistic/lib/clib.h":
     void normalise(double * m, int nxyz)