Introduce xbps_{pkgdb,rpool}_get_pkg_fulldeptree().

These routines return a xbps_array_t with a full sorted dependency graph
for the target pkg, by querying pkgdb or rpool.

Update xbps-query(8) to use the new libxbps API.

lib/rpool.c

@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2009-2013 Juan Romero Pardines.
+ * Copyright (c) 2009-2014 Juan Romero Pardines.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -287,6 +287,12 @@ xbps_rpool_get_pkg_revdeps(struct xbps_handle *xhp, const char *pkg)
 	return repo_find_pkg(xhp, pkg, REVDEPS_PKG);
 }
 
+xbps_array_t
+xbps_rpool_get_pkg_fulldeptree(struct xbps_handle *xhp, const char *pkg)
+{
+	return xbps_get_pkg_fulldeptree(xhp, pkg, true);
+}
+
 xbps_dictionary_t
 xbps_rpool_get_pkg_plist(struct xbps_handle *xhp,
 			 const char *pkg,