The purpose of this library is to use an md5() hash to secure a savefile from tampering,
in a manner which is not trivially circumvented.
This library defines three new procs:
Creates a new, protected savefile with the specified name from F.
Returns the newly-created, protected savefile.
The savefile F is left unmodified.
Creates a new savefile from the protected savefile F (created using safe_save()).
Returns the un-protected savefile, for reading.
The returned savefile can be read as normal, and is created as a temporary savefile.
Will return null if the savefile has been found to be tampered with.
Creates a hash from a text string. By default, will simply return md5("[world.hub_password][text]").
Should be overridden to use a more unique salt, if you do not feel that your hub password is secure.