MEDIUM: http: change the code returned by the response processing rule functions

MEDIUM: http: change the code returned by the response processing rule functions

Actually, this function returns a pointer on the rule that stop
the evaluation of the rule list. Later we integrate the possibility
of interrupt and resue the processsing of some actions. The current
response mode is not sufficient to returns the "interrupt" information.

The pointer returned is never used, so I change the return type of
this function by an enum. With this enum, the function is ready to
return the "interupt" value.