Add list structure definitions for liblvm objects.

- pv_t, vg_t, lv_t
- include libdevmapper.h: needed for struct dm_list

These list structures will be needed in later APIs to return a list of
handles to one object, given another object.  For example, lvm_vg_list_lvs()
will return a list of LV handles (lv_t's) given a VG handle (vg_t).  We
need a structure to do this so we define the LV structure, as well as the
other structures at this point.

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>

liblvm/lvm.h

@@ -15,6 +15,7 @@
 #define _LIB_LVM_H
 
 #include "lvm-version.h"
+#include "libdevmapper.h"
 
 #include <stdint.h>
 
@@ -28,6 +29,22 @@ typedef struct volume_group vg_t;
 typedef struct physical_volume pv_t;
 typedef struct logical_volume lv_t;
 
+typedef struct lvm_vg_list {
+	struct dm_list list;
+	vg_t *vg;
+} vg_list_t;
+
+typedef struct lvm_pv_list {
+	struct dm_list list;
+	pv_t *pv;
+} pv_list_t;
+
+typedef struct lvm_lv_list {
+	struct dm_list list;
+	lv_t *lv;
+} lv_list_t;
+
+
 struct lvm; /* internal data */
 
 /**