On Windows, don't encode filenames in the import machinery

Modules/symtablemodule.c

 #include "Python.h"
 
 #include "code.h"
 #include "Python-ast.h"
 #include "symtable.h"
 
 static PyObject *
 symtable_symtable(PyObject *self, PyObject *args)
 {
     struct symtable *st;
     PyObject *t;
 
     char *str;
-    char *filename;
+    PyObject *filename;
     char *startstr;
     int start;
 
-    if (!PyArg_ParseTuple(args, "sss:symtable", &str, &filename,
-                          &startstr))
+    if (!PyArg_ParseTuple(args, "sO&s:symtable",
+                          &str, PyUnicode_FSDecoder, &filename, &startstr))
         return NULL;
     if (strcmp(startstr, "exec") == 0)
         start = Py_file_input;
     else if (strcmp(startstr, "eval") == 0)
         start = Py_eval_input;
     else if (strcmp(startstr, "single") == 0)
         start = Py_single_input;
     else {
         PyErr_SetString(PyExc_ValueError,
            "symtable() arg 3 must be 'exec' or 'eval' or 'single'");
+        Py_DECREF(filename);
         return NULL;
     }
-    st = Py_SymtableString(str, filename, start);
+    st = Py_SymtableStringObject(str, filename, start);
+    Py_DECREF(filename);
     if (st == NULL)
         return NULL;
     t = st->st_blocks;
     Py_INCREF(t);
     PyMem_Free((void *)st->st_future);
     PySymtable_Free(st);
     return t;
 }
 
 static PyMethodDef symtable_methods[] = {
@@ skipping 50 matching lines @@
 
     PyModule_AddIntConstant(m, "SCOPE_OFF", SCOPE_OFFSET);
     PyModule_AddIntMacro(m, SCOPE_MASK);
 
     if (PyErr_Occurred()) {
         Py_DECREF(m);
         m = 0;
     }
     return m;
 }