[3.7] Fix misleading mentions of tp_size in comments. (GH-9136)

Many type object initializations labeled a field "tp_size" in the
comment, but the name of that field is tp_basicsize..
(cherry picked from commit 0e0bc4e221f592f305d335faf5f8046484eb9238)

Co-authored-by: Peter Eisentraut <peter@eisentraut.org>
diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index f594bda..16d3191 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -226,7 +226,7 @@
 static PyTypeObject Locktype = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)
     "_thread.lock",                     /*tp_name*/
-    sizeof(lockobject),                 /*tp_size*/
+    sizeof(lockobject),                 /*tp_basicsize*/
     0,                                  /*tp_itemsize*/
     /* methods */
     (destructor)lock_dealloc,           /*tp_dealloc*/
@@ -487,7 +487,7 @@
 static PyTypeObject RLocktype = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)
     "_thread.RLock",                    /*tp_name*/
-    sizeof(rlockobject),                /*tp_size*/
+    sizeof(rlockobject),                /*tp_basicsize*/
     0,                                  /*tp_itemsize*/
     /* methods */
     (destructor)rlock_dealloc,          /*tp_dealloc*/