Fix unexpected behavior of fft call on clongdouble type on win32

clongdouble dtype on Windows is of the same size of cdouble dtype,
hence attempt to convert array to cdouble type in PyArray_FROM_OTF
does not change the typenum.

The dispatch in mkl_fft assumes that typenum is either CDOUBLE or
CFLOAT for complex inputs, and hence a gap.

Set NPY_ENSURECOPY flag in the call to PyArray_FROM_OTF to ensure
that coercion results in typenum precisely either CFLOAT or CDOUBLE.

Author: oleksandr-pavlyk

mkl_fft/_pydfti.pyx

@@ -321,7 +321,7 @@ def _fft1d_impl(x, n=None, axis=-1, overwrite_arg=False, direction=+1, double fs
         # so we cast to complex double and operate in place
         try:
             x_arr = <cnp.ndarray> cnp.PyArray_FROM_OTF(
-                x_arr, cnp.NPY_CDOUBLE, cnp.NPY_BEHAVED)
+                x_arr, cnp.NPY_CDOUBLE, cnp.NPY_BEHAVED | cnp.NPY_ENSURECOPY)
         except:
             raise ValueError("First argument must be a complex or real sequence of single or double precision")
         x_type = cnp.PyArray_TYPE(x_arr)
@@ -545,7 +545,7 @@ def _rr_fft1d_impl2(x, n=None, axis=-1, overwrite_arg=False, double fsc=1.0):
     else:
         try:
             x_arr = <cnp.ndarray> cnp.PyArray_FROM_OTF(
-                x_arr, cnp.NPY_DOUBLE, cnp.NPY_BEHAVED)
+                x_arr, cnp.NPY_DOUBLE, cnp.NPY_BEHAVED | cnp.NPY_ENSURECOPY)
         except:
             raise TypeError("1st argument must be a real sequence")
         x_type = cnp.PyArray_TYPE(x_arr)
@@ -601,7 +601,7 @@ def _rr_ifft1d_impl2(x, n=None, axis=-1, overwrite_arg=False, double fsc=1.0):
         # so we cast to complex double and operate in place
         try:
             x_arr = <cnp.ndarray> cnp.PyArray_FROM_OTF(
-                x_arr, cnp.NPY_DOUBLE, cnp.NPY_BEHAVED)
+                x_arr, cnp.NPY_DOUBLE, cnp.NPY_BEHAVED | cnp.NPY_ENSURECOPY)
         except:
             raise ValueError("First argument should be a real or a complex sequence of single or double precision")
         x_type = cnp.PyArray_TYPE(x_arr)
@@ -669,7 +669,7 @@ def _rc_fft1d_impl(x, n=None, axis=-1, overwrite_arg=False, double fsc=1.0):
     else:
         # we must cast the input to doubles and allocate the output,
         try:
-            requirement = cnp.NPY_BEHAVED
+            requirement = cnp.NPY_BEHAVED | cnp.NPY_ENSURECOPY
             if x_type is cnp.NPY_LONGDOUBLE:
                 requirement = requirement | cnp.NPY_FORCECAST
             x_arr = <cnp.ndarray> cnp.PyArray_FROM_OTF(