Refactor code to remove WEP_FLAG_SPECIALATTACK checks if WEP_FLAG_HIDDEN is already...

Refactor code to remove WEP_FLAG_SPECIALATTACK checks if WEP_FLAG_HIDDEN is already checked.

This refactoring is now possible thanks to the changes of !1344, where all WEP_FLAG_SPECIALATTACK checks have been paired with WEP_FLAG_HIDDEN checks

To make sure WEP_FLAG_HIDDEN is always set on special attacks, weapon initialization code triggers a fatal error if WEP_FLAG_SPECIALATTACK is set but WEP_FLAG_HIDDEN is not.