PTH: Added minor 'sibling jumping' optimization for iterating over the side table used for fast preprocessor block skipping.  This has a minor performance improvement when preprocessing Cocoa.h, but can have some wins in pathologic cases.
PTH: Added minor 'sibling jumping' optimization for iterating over the side table used for fast preprocessor block skipping.  This has a minor performance improvement when preprocessing Cocoa.h, but can have some wins in pathologic cases.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@60966 91177308-0d34-0410-b5e6-96231b3b80d8

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