compression: re-compute the uri after rebuilding the buffer

When freeing the buffer in be3b603, the URI in transaction remained
pointing to the old buffer. Therefore when building local ACK or CANCEL,
URI was having garbage.

Fixes #1575

Many thanks to Jock McKechnie for reporing it and offering testing support

modules/compression/compression.c

@@ -311,6 +311,9 @@ void wrap_tm_func(struct cell* t, int type, struct tmcb_params* p)
 
 	t->uac[p->code].request.buffer.s = buf;
 	t->uac[p->code].request.buffer.len = olen;
+	/* we also need to compute the uri so that it points within the new buffer */
+	t->uac[p->code].uri.s = buf + t->method.len + 1;
+	/* uri.len should be the same, since it is not changed by compression */
 }
 
 int wrap_msg_compress(str* buf, struct sip_msg* p_msg) {