NFC: Move VisitExpr code to dumpStmt
NFC: Move VisitExpr code to dumpStmt

Summary:
The call is duplicated in the handlers of all Expr subclasses.

This change makes it easy to split statement handling out to
TextNodeDumper.

Reviewers: aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D55339

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@348546 91177308-0d34-0410-b5e6-96231b3b80d8

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