Work around bug in mingw-w64 GCC 8.1.0
Work around bug in mingw-w64 GCC 8.1.0

This particular version of GCC seems to break bitfields when a method
appears between two bitfield members.

Personally, I think it's nice to keep bitfields close together so that
it's easy to check how things are packed, so I moved the method after
SubClassData.

Fixes PR38168.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@337495 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm