partially re-enabled the numpy import function hack - only import_umath() is problematic

tests/run/numpy_common.pxi

-# (disabled) hack to avoid C compiler warnings about unused functions in the NumPy header files
+# hack to avoid C compiler warnings about unused functions in the NumPy header files
 
-##cdef extern from *:
-##   bint FALSE "0"
-##   void import_array()
-##   void import_umath1(void* ret)
-##
-##if FALSE:
-##    import_array()
-##    import_umath1(NULL)
+cdef extern from *:
+   bint FALSE "0"
+   void import_array()
+#   void import_umath()
+
+if FALSE:
+    import_array()
+#    import_umath()