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

tools/llvmc/llvmc.cpp

@@ -368,4 +368,5 @@ int main(int argc, char **argv) {
   } catch (...) {
     std::cerr << argv[0] << ": Unexpected unknown exception occurred.\n";
   }
+  return 1;
 }