use numpy compat isnan

Author: chris-b1

pandas/_libs/window.pyx

@@ -6,7 +6,6 @@ from cython cimport Py_ssize_t
 from libcpp.deque cimport deque
 
 from libc.stdlib cimport malloc, free
-from libc.math cimport isnan
 
 import numpy as np
 cimport numpy as cnp
@@ -18,6 +17,9 @@ cdef extern from "src/headers/cmath" namespace "std":
     int signbit(double) nogil
     double sqrt(double x) nogil
 
+cdef extern from "numpy/npy_math.h":
+    bint isnan(double) nogil
+
 cimport util
 from util cimport numeric