Clean up doxygen comments in FunctionAttrs, promoting some non-doxygen comments, deleting duplicate comments, moving comments to consistently live on the definition since these are all really internal routines, etc. NFC.
Clean up doxygen comments in FunctionAttrs, promoting some non-doxygen
comments, deleting duplicate comments, moving comments to consistently
live on the definition since these are all really internal routines,
etc. NFC.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@247520 91177308-0d34-0410-b5e6-96231b3b80d8

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