Fix UseAuto not transforming iterator when non-fully qualifiers are used and
using inline namespaces is specified.

UseAuto used to fail to transform iterators when using inline namespaces and
non-fully qualified types, relying on a using directive previously declared.
- This fix uses the already define isFromStdNamespace matcher.
- Fixed tests and added a new test using inline namespaces.
- Added CustomMatchers to reuse common matchers among transforms.


git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@186327 91177308-0d34-0410-b5e6-96231b3b80d8