Workaround ASTMatcher crashes. Added some more test cases.

Summary:
- UsingDecl matcher crashed when `UsingShadowDecl` has no parent map. Workaround by moving parent check into `UsingDecl`.
- FunctionDecl matcher crashed when there is a lambda defined in parameter list (also due to no parent map).
  Workaround by putting `unless(cxxMethodDecl())` before parent check.

Reviewers: klimek, sbenza, aaron.ballman, hokein

Subscribers: aaron.ballman, cfe-commits

Differential Revision: https://reviews.llvm.org/D24862

llvm-svn: 282486