[ASTMatchers] Introduce a matcher for `ObjCIvarExpr`, support getting it's declaration
[ASTMatchers] Introduce a matcher for `ObjCIvarExpr`, support getting it's declaration

ObjCIvarExpr is *not* a subclass of MemberExpr, and a separate matcher
is required to support it.
Adding a hasDeclaration support as well, as it's not very useful without
it.

Differential Revision: https://reviews.llvm.org/D49701

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@338140 91177308-0d34-0410-b5e6-96231b3b80d8

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