Add support for the Shearwater Petrel 2.

The Shearwater Petrel 2 uses exactly the same communication protocol as
the original Petrel. Therefore the new model has always been supported
out, and we only need to add the new model to the list of supported
devices.

src/descriptor.c

@@ -236,6 +236,7 @@ static const dc_descriptor_t g_descriptors[] = {
 	{"Shearwater", "Predator", DC_FAMILY_SHEARWATER_PREDATOR, 2},
 	/* Shearwater Petrel */
 	{"Shearwater", "Petrel",   DC_FAMILY_SHEARWATER_PETREL, 3},
+	{"Shearwater", "Petrel 2", DC_FAMILY_SHEARWATER_PETREL, 3},
 	/* Dive Rite NiTek Q */
 	{"Dive Rite", "NiTek Q",   DC_FAMILY_DIVERITE_NITEKQ, 0},
 	/* Citizen Hyper Aqualand */