Use hook_token_info() to provide info on which tokens are 'URLs'

Currently we rely on the magical token naming convention of -path and -alias suffixes to skip certain processing, like removing backslashes, etc. I think we should probably use core's hook_token_info and put the definition of which tokens are URLs directly in the token's description array.

For instance:

pathauto_token_info_alter(&$info) {
  $info['tokens']['node']['url']['url'] = TRUE;
  $info['tokens']['menu']['path']['url'] = TRUE;
}