* Demoted the asterisk to a regular symbol (not a wildcard) in
  version_tokens_delete()
* version_tokens_delete() now trims whitespace around individual token
  names to delete.
* version_tokens_delete() will ignore an invalid (empty, all spaces)
  token name.
* version_tokens_delete() will treat NULL arguments as an empty string
  argument.
* version_tokens_set() and version_tokens_edit() will properly detect
  and ignore empty token names
* version_tokens_lock_shared() and version_tokens_lock_exclusive()
  will now return error for NULL timeout values.
* Test cases added to the above and existing tests updated.