Add a sanity check in the Redeclarable::redecl_iterator to avoid infinite loop when we formed an invalid redeclaration chain due to a bug.
Add a sanity check in the Redeclarable::redecl_iterator to avoid infinite loop
when we formed an invalid redeclaration chain due to a bug.

Thanks to Doug for the hint!

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@146816 91177308-0d34-0410-b5e6-96231b3b80d8

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