When we are deserializing the lexical decls of a DeclContext from PCH, notify the PCHReader to hold off passing Decls to the consumer until the DeclContext is fully prepared.
When we are deserializing the lexical decls of a DeclContext from PCH, notify the PCHReader to hold off passing Decls
to the consumer until the DeclContext is fully prepared.

Before, due to recursive loading, we could be in a situation where we would try to deserialize the decls of a DeclContext which was already doing that, and bad things would happen. In the specific case I encountered, the lexical decls would
form a cycle and we would enter infinite loop territory.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@109857 91177308-0d34-0410-b5e6-96231b3b80d8

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