Fix typo in dtype_transfer
 - _strided_to_strided_one_to_n_with_finish is missing a d-> when
   initializing data_finish_src
Fix proper handling of NaNs in allclose in core/numeric.
 - The comment in allclose says "If either array contains one or more
   NaNs, False is returned." but this is not done properly. Some
   compilers have problem with abs and NaNs.
Fix two occurences of use-before-initialized.
 - core/src/multiarray/dtype_transfer.c
   _strided_to_strided_string_to_datetime, initialize dt.
 - core/src/umath/ufunc_object.c PyUFunc_Reduceat, initialize
   need_outer_iterator.
Fix nc_pow@c@ so it uses an optimizer safe way to raise FE_INVALID.
 - The original code tried to do a simple subtraction, the result of
   which was just discarded. Optimizers throws that away and the raise
   never happend.
Add support for using openblas for the _dotblas function.
 - openblas is usually a lot faster then ATLAS so make sure it can get
   correctly detected.