Implement relate for code object and fix its test in test_Path.py

Some referenced attributes are no longer slotted. I'm not sure
how to get a fallback to default relate for slotted attributes
so I'm just going to make relate do the entire thing.

For #41

guppy/heapy/test/test_Path.py

@@ -67,8 +67,12 @@ def f():
         # xxx brittle test but catches a bug
         self.chkpath(co, 3, '%s.co_consts[1]')
         # commented in notes Sep 27 2004
-        relAttr = ('co_code', 'co_consts', 'co_names', 'co_varnames',
-                   'co_freevars', 'co_cellvars', 'co_filename', 'co_name')
+        relAttr = ('co_code', 'co_consts', 'co_names',
+                   'co_filename', 'co_name')
+        if self.version_info < (3, 11):
+            relAttr += ('co_varnames', 'co_freevars', 'co_cellvars')
+        else:
+            relAttr += ('co_exceptiontable', 'co_qualname')
         if self.version_info >= (3, 10):
             relAttr += ('co_linetable',)
         else:

src/heapy/stdtypes.c

@@ -419,6 +419,42 @@ code_traverse(NyHeapTraverse *ta) {
     return 0;
 }
 
+static int
+code_relate(NyHeapRelate *r)
+{
+    PyCodeObject *v = (void *)r->src;
+#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 11
+    RENAMEATTR(_co_code, co_code);
+#else
+    ATTR(co_code);
+#endif
+    ATTR(co_consts);
+    ATTR(co_names);
+#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 11
+    ATTR(co_exceptiontable);
+#endif
+#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 11
+    INTERATTR(co_localsplusnames);
+    INTERATTR(co_localspluskinds);
+#else
+    ATTR(co_varnames);
+    ATTR(co_freevars);
+    ATTR(co_cellvars);
+#endif
+    ATTR(co_filename);
+    ATTR(co_name);
+#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 11
+    ATTR(co_qualname);
+#endif
+#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 10
+    ATTR(co_linetable);
+#else
+    ATTR(co_lnotab);
+#endif
+    ATTR(co_weakreflist);
+    return 0;
+}
+
 /* type_traverse adapted from typeobject.c from 2.4.2
    except:
    * I removed the check for heap type
@@ -542,7 +578,7 @@ NyHeapDef NyStdTypes_HeapDef[] = {
         0,             /* type */
         0,             /* size */
         code_traverse, /* traverse */
-        0              /* relate */
+        code_relate    /* relate */
     }, {
         0,             /* flags */
         0,             /* type */