add test for cfunc auto-wrapping at module level

tests/run/cfunc_convert.pyx

 # mode: run
 # cython: always_allow_keywords=True
 
+cimport cython
 
 from libc.math cimport sqrt
 
@@ -56,6 +57,22 @@ def return_libc_sqrt():
     return sqrt
 
 
+global_csqrt = sqrt
+
+def test_global():
+    """
+    >>> global_csqrt(9)
+    3.0
+    >>> global_csqrt.__doc__
+    'wrap(x: float) -> float'
+    >>> test_global()
+    double (double) nogil
+    Python object
+    """
+    print cython.typeof(sqrt)
+    print cython.typeof(global_csqrt)
+
+
 cdef long long rad(long long x):
     cdef long long rad = 1
     for p in range(2, <long long>sqrt(x) + 1):