Updated the AST importer to support importing LinkageSpecDecls.  This is relevant when LLDB wants to import Decls from non-C++ modules, since many declarations are in extern "C" blocks.
Updated the AST importer to support importing
LinkageSpecDecls.  This is relevant when LLDB
wants to import Decls from non-C++ modules,
since many declarations are in extern "C"
blocks.


git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@223860 91177308-0d34-0410-b5e6-96231b3b80d8

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