silver vs lycanthropy (trunk only)

silver vs lycanthropy (trunk only)

     Monster werecritters are vulnerable to silver when in human form as
well as when in beast form, but hero inflicted with lycanthropy was only
vulnerable while in beast form.  Add pseudo-property Hate_silver to handle
that correctly.  Also, add silver vulnerability to enlightenment feedback.
Lastly, hero vulnerable to silver had Con abused if hit by silver missile
but not when hit hand-to-hand; add an exercise() call to the latter.