Fix a couple of signed/unsigned comparison warnings

Objects/floatobject.c

@@ -884,7 +884,7 @@ PyFloat_Fini(void)
 {
 	PyFloatObject *p;
 	PyFloatBlock *list, *next;
-	int i;
+	unsigned i;
 	int bc, bf;	/* block count, number of freed blocks */
 	int frem, fsum;	/* remaining unfreed floats per block, total */
 

Python/codecs.c

@@ -804,7 +804,7 @@ static int _PyCodecRegistry_Init(void)
 
     PyInterpreterState *interp = PyThreadState_GET()->interp;
     PyObject *mod;
-    int i;
+    unsigned i;
 
     if (interp->codec_search_path != NULL)
 	return 0;