Introduce a new tool_output_file class, which extends raw_ostream with

Introduce a new tool_output_file class, which extends raw_ostream with
functionality that most command-line tools need: ensuring that the
output file gets deleted if the tool is interrupted or encounters an
error.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111595 91177308-0d34-0410-b5e6-96231b3b80d8