[index] Avoid using a RecursiveASTVisitor for SyntacticFormIndexer and iterate the DesignatedInitExprs of the InitListExpr directly.
[index] Avoid using a RecursiveASTVisitor for SyntacticFormIndexer and iterate the DesignatedInitExprs of the InitListExpr directly.

This is more efficient, as per feedback by Richard.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@285666 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang