For PR351:

For PR351:
* Place a try/catch block around the entire tool to Make sure std::string
  exceptions are caught and printed before exiting the tool.
* Make sure we catch unhandled exceptions at the top level so that we don't
  abort with a useless message but indicate than an unhandled exception was
  generated.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19192 91177308-0d34-0410-b5e6-96231b3b80d8