Make a couple of helper classes private to TypoCorrectionConsumer.
Make a couple of helper classes private to TypoCorrectionConsumer.

The SpecifierInfo and NamespaceSpecifierSet are now only used by
TypoCorrectionConsumer, so treat them as the implementation details of
TypoCorrectionConsumer that they are. Also make NamespaceSpecifierSet's
method names more style guide compliant.

No functionality changed.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@210671 91177308-0d34-0410-b5e6-96231b3b80d8

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