Add new parser error code, E_OVERFLOW. This error is returned when

the number of children of a node exceeds the max possible value for
the short that is used to count them.  The Python runtime converts
this parser error into the SyntaxError "expression too long."

Include/errcode.h

@@ -52,6 +52,7 @@ PERFORMANCE OF THIS SOFTWARE.
 #define E_DONE		16	/* Parsing complete */
 #define E_ERROR		17	/* Execution error */
 #define E_INDENT	18	/* Invalid indentation detected */
+#define E_OVERFLOW      19      /* Node had too many children */
 
 #ifdef __cplusplus
 }