object: speed up type verification by not relying on strcmp()

Instead of using string contents for type identification use the address
of a constant string array. This should speed up type verifications a
little sind we only need to compare one machine word instead of a full
string. Also, this saves a few strings.

To make clear that types must be compared via address and not string
contents 'type_name' is now called 'type_id'.

This also simplifies the macros for declaring and defining public and
private subclasses.

src/pulsecore/protocol-esound.c

@@ -120,9 +120,8 @@ typedef struct connection {
     pa_time_event *auth_timeout_event;
 } connection;
 
-PA_DECLARE_CLASS(connection);
+PA_DEFINE_PRIVATE_CLASS(connection, pa_msgobject);
 #define CONNECTION(o) (connection_cast(o))
-static PA_DEFINE_CHECK_TYPE(connection, pa_msgobject);
 
 struct pa_esound_protocol {
     PA_REFCNT_DECLARE;