[ABI] Added signedAsData bit to method descriptor flags.
[ABI] Added signedAsData bit to method descriptor flags.

It is necessary to determine whether a given method in a vtable or a
witness table ought to be signed as data or as code.  For example, async
functions pointers must be signed as data.

ahoppen/swift,tkremenek/swift,xwu/swift,parkera/swift,JGiola/swift,parkera/swift,benlangmuir/swift,gregomni/swift,glessard/swift,JGiola/swift,gregomni/swift,parkera/swift,glessard/swift,ahoppen/swift,apple/swift,tkremenek/swift,tkremenek/swift,glessard/swift,roambotics/swift,hooman/swift,hooman/swift,apple/swift,atrick/swift,hooman/swift,roambotics/swift,apple/swift,glessard/swift,roambotics/swift,JGiola/swift,xwu/swift,atrick/swift,parkera/swift,JGiola/swift,hooman/swift,benlangmuir/swift,ahoppen/swift,gregomni/swift,tkremenek/swift,glessard/swift,tkremenek/swift,atrick/swift,xwu/swift,parkera/swift,parkera/swift,ahoppen/swift,xwu/swift,benlangmuir/swift,ahoppen/swift,JGiola/swift,atrick/swift,apple/swift,benlangmuir/swift,roambotics/swift,rudkx/swift,parkera/swift,rudkx/swift,atrick/swift,rudkx/swift,atrick/swift,ahoppen/swift,glessard/swift,rudkx/swift,xwu/swift,roambotics/swift,rudkx/swift,gregomni/swift,tkremenek/swift,hooman/swift,tkremenek/swift,xwu/swift,benlangmuir/swift,apple/swift,xwu/swift,benlangmuir/swift,hooman/swift,hooman/swift,parkera/swift,rudkx/swift,apple/swift,roambotics/swift,gregomni/swift,JGiola/swift,gregomni/swift