packet: Make pa_packet_new() create fixed-size packets

if length exceeds maximum appended size, create a packet of
type dynamic instead of type appended

this is a preparation to use a separate free-list for packets

document semantics of pa_packet_new_*() functions

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>

src/pulsecore/packet.h

@@ -25,7 +25,12 @@
 
 typedef struct pa_packet pa_packet;
 
+/* create empty packet (either of type appended or dynamic depending
+ * on length) */
 pa_packet* pa_packet_new(size_t length);
+
+/* data must have been malloc()ed; the packet takes ownership of the memory,
+ * i.e. memory is free()d with the packet */
 pa_packet* pa_packet_new_dynamic(void* data, size_t length);
 
 const void* pa_packet_data(pa_packet *p, size_t *l);