[clang-format] Move OriginalPrefix from base to subclass.
[clang-format] Move OriginalPrefix from base to subclass.

Summary:
OriginalPrefix is only needed for line comment sections. Moved from the base class to the child class.
No functional changes.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D29716

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@294457 91177308-0d34-0410-b5e6-96231b3b80d8

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