In space, no one can hear you shriek

Or chimper for that matter. Also fixes deaf people hearing vox shriek.
Improves the implementation of non-verbal languages

Cleans out the nonverbal language check from say_understands(), which
now is responsible for language only.
Nonverbal languages have a chance of causing an emote when used.
Adds sign languages, which have no verbal component.
Adds workaround for PHP whitelist

Apparently there's some PHP script that needs to be updated or
something. Revert this once that is done.
Tweaks nonverbal emote frequency
Removes taj whisker emote
Merge pull request #5389 from mwerezak/sign-lang

Improves non-verbal furry languages, fixes vox shriek playing for deaf people and in space