Use macro versions instead of function versions when we already know the type.
This will hopefully get rid of some Coverity warnings, be a hint to
developers, and be marginally faster.

Some asserts were added when the type is currently known, but depends
on values from another function.
diff --git a/Modules/stropmodule.c b/Modules/stropmodule.c
index cffef3a..2f671b6 100644
--- a/Modules/stropmodule.c
+++ b/Modules/stropmodule.c
@@ -942,7 +942,7 @@
 	}
 
 	table = table1;
-	inlen = PyString_Size(input_obj);
+	inlen = PyString_GET_SIZE(input_obj);
 	result = PyString_FromStringAndSize((char *)NULL, inlen);
 	if (result == NULL)
 		return NULL;