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/play-memblockq.c

@@ -47,9 +47,8 @@ enum {
     MEMBLOCKQ_STREAM_MESSAGE_UNLINK,
 };
 
-PA_DECLARE_CLASS(memblockq_stream);
+PA_DEFINE_PRIVATE_CLASS(memblockq_stream, pa_msgobject);
 #define MEMBLOCKQ_STREAM(o) (memblockq_stream_cast(o))
-static PA_DEFINE_CHECK_TYPE(memblockq_stream, pa_msgobject);
 
 static void memblockq_stream_unlink(memblockq_stream *u) {
     pa_assert(u);