Suggested change to PICS spec

The following has been added to http://www.w3.org/PICS/update.html:

Allow "~" in transmission names. 
     The SafeSurf system uses this as part of its naming scheme and
     has requested that it be added to the syntax of both label lists
     and machine-readable descriptions of rating services. Since it
     does not impact any existing protocols, this addition is
     straightforward: "alphanumpm" in both the machine-readable
     description and the label list syntax must be extended to include
     "~".

--Jim