[Frontend] Attach comments to decls when emitting .swiftsourceinfo
[Frontend] Attach comments to decls when emitting .swiftsourceinfo

.swiftsourceinfo contains comment ranges, so parsing should attach
comments when it is being emitted. Generally this turned out to be fine
because .swiftdoc is usually output as well, but when calling
swift-frontend directly in tests that isn't necessarily the case.

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