Don't initialize repository pool via xbps_init, instead in repository_pool public funcs.

That way we can avoid having to sync all remote repositories for any code
using xbps_init()!

include/xbps_api.h

@@ -259,7 +259,6 @@ struct xbps_handle {
  *   - Initialize the debug printfs.
  *   - Internalize the proplib dictionary in config file.
  *   - Internalize the regpkgdb dictionary (if available).
- *   - Initialize the repository pool interface (if available).
  *
  * @param[in] xh Pointer to an xbps_handle structure. It's
  * assumed that this pointer is not NULL.