[clang-tidy] Avoid incorrect fixes in modernize-use-using

Avoid fixes for typedefs with multiple types and for typedefs with struct
definitions. Partially addresses http://llvm.org/PR28334

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@292918 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed