Sort Attributes by "HeaderName" 
Sort Attributes by "HeaderName" 

Attributes in the docs were previously sorted (apparently)
by the attribute name, so AnyX86Interrupt ended up being the
first one, rather than in a meaningful place. This resulted in the
4 'interrupt' titled sections being all in different places.

This replaces it with a naive alphabetical sort (case sensitive, underscore
and special characters first, etc).

Differential Revision: https://reviews.llvm.org/D38969


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@315931 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang