repo: introduce xbps_repo_release(), misc changes.

- xbps_repo_release(): new function to release all resources
  associated with a repository object.

- xbps_repo_close(): this now just closes the file descriptor
  associated with the archive and associated resources.

- repo_open_local: after getting the repository dictionaries,
  use xbps_repo_close() to release archive resources.

Bump XBPS_API_VERSION.

include/xbps.h.in

@@ -51,7 +51,7 @@
  *
  * This header documents the full API for the XBPS Library.
  */
-#define XBPS_API_VERSION	"20200221"
+#define XBPS_API_VERSION	"20200414"
 
 #ifndef XBPS_VERSION
  #define XBPS_VERSION		"UNSET"
@@ -1645,12 +1645,21 @@ struct xbps_repo *xbps_repo_stage_open(struct xbps_handle *xhp, const char *url)
 struct xbps_repo *xbps_repo_public_open(struct xbps_handle *xhp, const char *url);
 
 /**
- * Closes a repository object and releases resources.
+ * Closes a repository object, its archive associated is
+ * closed and those resources released.
  *
  * @param[in] repo The repository object to close.
  */
 void xbps_repo_close(struct xbps_repo *repo);
 
+/**
+ * This calls \fn xbps_repo_close and releases all resources
+ * associated with this repository object.
+ *
+ * @param[in] repo The repository object to release.
+ */
+void xbps_repo_release(struct xbps_repo *repo);
+
 /**
  *
  * Returns a heap-allocated string with the repository local path.