Don't error out when non-const value is passed as a const specified

parameter to a function. When function arguments are marked as const,
this means that the function should not modify them, not that
non-const arguments are not allowed.
This also fixes a test that began failing because this change resulted
in a slightly different error message when conversion to a const
qualified argument is not possible.

Cython/Compiler/ExprNodes.py

@@ -5052,6 +5052,8 @@ class SimpleCallNode(CallNode):
         for i in range(min(max_nargs, actual_nargs)):
             formal_arg = func_type.args[i]
             formal_type = formal_arg.type
+            if formal_type.is_const:
+                formal_type = formal_type.const_base_type
             arg = args[i].coerce_to(formal_type, env)
             if formal_arg.not_none:
                 # C methods must do the None checks at *call* time

tests/errors/cpp_no_auto_conversion.pyx

@@ -19,5 +19,5 @@ cdef long long e = constructor_overload(17)
  
 
 _ERRORS = u"""
-18:40: Cannot assign type 'long' to 'const wrapped_int'
+18:40: Cannot assign type 'long' to 'wrapped_int'
 """