Improve xbps_end() and use it before exit(3)ing.

- Simplify xbps_repo_open::repo_get_dict().
- Use xbps_end() in the utils where necessary.
- Make xbps_end() call xbps_pkgdb_unlock() if necessary.
- Make xbps_end() release rpool resources.
- Make xbps_end() release resources from xbps_handle.
- Fixed 90% of reported leaks (still reachable at exit) from valgrind.

That was to silence valgrind's memcheck with --leak-check=full.

lib/rpool.c

@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2009-2014 Juan Romero Pardines.
+ * Copyright (c) 2009-2015 Juan Romero Pardines.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -91,6 +91,20 @@ xbps_rpool_get_repo(const char *url)
 	return NULL;
 }
 
+void
+xbps_rpool_release(struct xbps_handle *xhp _unused)
+{
+	struct xbps_repo *repo;
+
+	while ((repo = SIMPLEQ_FIRST(&rpool_queue))) {
+	       SIMPLEQ_REMOVE(&rpool_queue, repo, xbps_repo, entries);
+	       xbps_repo_close(repo, true);
+	       free(repo);
+	}
+	if (xhp->repositories)
+		xbps_object_release(xhp->repositories);
+}
+
 int
 xbps_rpool_foreach(struct xbps_handle *xhp,
 	int (*fn)(struct xbps_repo *, void *, bool *),