Support "unusable=1" parameter in SpellInfo().
Support "unusable=1" parameter in SpellInfo().

This allows us to flag a spell as unusable at compile-time.

eXhausted/Ovale,eXhausted/Ovale,ultijlam/ovale,eXhausted/Ovale,ultijlam/ovale,ultijlam/ovale,Xeltor/ovale