[llvm-cxxfilt] Use llvm::outs(). Simplify.

This adds a dependency on Support/. As llvm-cxxfilt will grow
support for options this will be needed anyway.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282523 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed