Fix error positions of undefined builtins and constants

[orivej]

Currently Cython generates code like this:

 int __Pyx_InitCachedBuiltins(void) {
     __pyx_builtin_NAME = __Pyx_GetBuiltinName(...);
     if (!__pyx_builtin_NAME) __PYX_ERR(1, 44, __pyx_L1_error)
 }

 int __pyx_pymod_exec_MODULE(PyObject *__pyx_pyinit_module) {
     if (__Pyx_InitCachedBuiltins() < 0) __PYX_ERR(1, 1, __pyx_L1_error)
 }

When InitCachedBuiltins and InitCachedConstants call __PYX_ERR, they
pass the file and line where a builtin is used, but then pymod_exec
overwrites it with 1 and 1, and the error message looks like this:

   File "FILE", line 1, in init MODULE.
     import os
 NameError: name 'NAME' is not defined

After this change Cython generates:

 int __pyx_pymod_exec_MODULE(PyObject *__pyx_pyinit_module) {
     if (__Pyx_InitCachedBuiltins() < 0) goto __pyx_L1_error;
 }

and prints:

   File "FILE", line 44, in init MODULE.
     print(NAME)
 NameError: name 'NAME' is not defined

[scoder]

Thanks