Fix UseAuto replacing declaration lists with new expressions

UseAuto used to replace declarion lists with new expressons where some
variable were not initialized with new.
This fix checks that every DeclStmt has a VarDecl with an initializer and it
also ensures that all declarations have the same type.

Added tests for multiple declarations and for typedefs.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@182736 91177308-0d34-0410-b5e6-96231b3b80d8