memblockq: Improve debuggability by storing a name and a sample spec.

These are not used for anything at this point, but this
makes it easy to add ad-hoc debug prints that show the
memblockq name and to convert between bytes and usecs.

src/modules/rtp/module-rtp-send.c

@@ -348,10 +348,11 @@ int pa__init(pa_module*m) {
     u->source_output = o;
 
     u->memblockq = pa_memblockq_new(
+            "module-rtp-send memblockq",
             0,
             MEMBLOCKQ_MAXLENGTH,
             MEMBLOCKQ_MAXLENGTH,
-            pa_frame_size(&ss),
+            &ss,
             1,
             0,
             0,