Issue #3080: Use PyUnicode_InternFromString() for builtins

_PyImport_FixupBuiltin() and _PyImport_FindBuiltin() use
PyUnicode_InternFromString() instead of PyUnicode_FromString().
diff --git a/Python/import.c b/Python/import.c
index 597ef43..d43b881 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -625,7 +625,7 @@
 {
     int res;
     PyObject *nameobj;
-    nameobj = PyUnicode_FromString(name);
+    nameobj = PyUnicode_InternFromString(name);
     if (nameobj == NULL)
         return -1;
     res = _PyImport_FixupExtensionObject(mod, nameobj, nameobj);
@@ -681,7 +681,7 @@
 _PyImport_FindBuiltin(const char *name)
 {
     PyObject *res, *nameobj;
-    nameobj = PyUnicode_FromString(name);
+    nameobj = PyUnicode_InternFromString(name);
     if (nameobj == NULL)
         return NULL;
     res = _PyImport_FindExtensionObject(nameobj, nameobj);