partition: add partition type getset

Partition type getset enables modifying and getting the type
of a give libfdisk partition.

The type of a partition is defined using PartType, which
can only be instanced via label specific functions
get_parttype_from_string or get_parttype_from_code.

For example, to set the type of a new partitions to 'EFI System':

>>> import fdisk
>>> pa = fdisk.Partition()
>>> pa.type
>>> cxt = fdisk.Context('./disk.bin', readonly=False)
>>> cxt.create_disklabel('gpt')
>>> efitype = cxt.label.get_parttype_from_string("c12a7328-f81f-11d2-ba4b-00a0c93ec93b")
>>> pa.type = efitype

Following the previous example, getting its current partition type:

>>> pa.type
<libfdisk.PartType object at 0x7f2f0a9a12d0, name=EFI System>

partition.c

@@ -143,9 +143,40 @@ static int Partition_set_size(PartitionObject *self, PyObject *value, void *clos
 
 	return 0;
 }
+static PyObject *Partition_get_type(PartitionObject *self)
+{
+	struct fdisk_parttype *t;
+
+	t = fdisk_partition_get_type(self->pa);
+	if (t)
+		return PyObjectResultPartType(t);
+
+	Py_RETURN_NONE;
+}
+static int Partition_set_type(PartitionObject *self, PyObject *value, void *closure)
+{
+	if (!value) {
+		PyErr_SetString(PyExc_TypeError,
+				"partition type assertion error");
+		return -1;
+	}
+	if (!PyObject_TypeCheck(value, &PartTypeType)) {
+		PyErr_SetString(PyExc_TypeError,
+				"invalid partition type");
+		return -1;
+	}
+	if (fdisk_partition_set_type(self->pa, ((PartTypeObject *) value)->type) < 0) {
+		PyErr_SetString(PyExc_TypeError,
+				"libfdisk reported error setting partition type");
+		return -1;
+	}
+
+	return 0;
+}
 static PyGetSetDef Partition_getseters[] = {
 	{"partno",	(getter)Partition_get_partno, (setter)Partition_set_partno, "partition number", NULL},
 	{"size",	(getter)Partition_get_size, (setter)Partition_set_size, "number of sectors", NULL},
+	{"type",	(getter)Partition_get_type, (setter)Partition_set_type, "number of sectors", NULL},
 	{NULL}
 };