When adding a visible decl, deserialize the visible decls and add it.
When adding a visible decl, deserialize the visible decls and add it.

Before this commit, visible decls added before deserialization were ignored.
This was not an issue since name lookup (that usually comes before the addition) forces deserialization
but it is an issue for lazily declared class implicit members.

We can use a PCH'ed <string> now.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@107596 91177308-0d34-0410-b5e6-96231b3b80d8

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