Make ToolExecutionError inherit std::exception and implement its
interface: getMessage() is gone, use what() instead.

llvm-svn: 11621
diff --git a/llvm/tools/bugpoint/bugpoint.cpp b/llvm/tools/bugpoint/bugpoint.cpp
index 3c89dce..65de965 100644
--- a/llvm/tools/bugpoint/bugpoint.cpp
+++ b/llvm/tools/bugpoint/bugpoint.cpp
@@ -54,7 +54,7 @@
   try {
     return D.run();
   } catch (ToolExecutionError &TEE) {
-    std::cerr << "Tool execution error: " << TEE.getMessage() << "\n";
+    std::cerr << "Tool execution error: " << TEE.what() << "\n";
     return 1;
   } catch (...) {
     std::cerr << "Whoops, an exception leaked out of bugpoint.  "