STARTREK enable alternative path for voc files

[Retro64]

When installing the GOG version or browsing the CD version, the voc folder is on the same level as the language folders. All localizations access this parent folder in order to use use the same voc files. Currently the engine searches - naturally - for the voc files in the root folder of each language. For sure the files can be copied redundant into each folder or a symlink might be used within *NIX systems to get rid of the redundant files, but an option to search the parent folder for voc folder or a config options to configure the path to the voc folders might be a useful feature for multi-language game support.