Add a test for namespaced struct with memoryview

tests/compile/cpp_structs.pyx

 # tag: cpp
 # mode: compile
 
+from cython.view import array
+
 cdef extern from "point.h" namespace "geometry":
 
     cdef struct Point:
@@ -10,3 +12,5 @@ cdef extern from "point.h" namespace "geometry":
 
 cdef Point p = Point(0.0, 0.0, 0)
 the_point = p
+
+cdef Point[::1] ps = array((10,), itemsize=sizeof(Point), format='ddi')