Return a proper null CXSourceLocation from clang_getLocation() when the SourceLocation is invalid.  Fixes <rdar://problem/8056640>.
Return a proper null CXSourceLocation from clang_getLocation() when the SourceLocation is invalid.  Fixes <rdar://problem/8056640>.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@105392 91177308-0d34-0410-b5e6-96231b3b80d8

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