Made a bunch of cleanups, as per Chris' recommendations:

* Removed unused global and member variables
* Fixed comments (CodeGeneratorBug.cpp)
* Check for possibly failing GCC::create() and CBE::create()
* Remove generated files after diffing the output (e.g., shared object)
* Instead of using std::for_each, use explicit loops as std::for_each may
  duplicate the functor, and ours carries state
* Changed member var from cl::opt<std::string> to just std::string
* Fixed doxygen comments
* Fixed string comparisons to use [ str.empty() ] instead of [ str == "" ]
* Cache instances of CBE and GCC in BugDriver across compilations and executions
  while testing tools.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7302 91177308-0d34-0410-b5e6-96231b3b80d8

tools/bugpoint/BugDriver.cpp

@@ -66,7 +66,7 @@ void DeleteFunctionBody(Function *F) {
 
 BugDriver::BugDriver(const char *toolname)
   : ToolName(toolname), ReferenceOutputFile(OutputFile),
-    Program(0), Interpreter(0) {}
+    Program(0), Interpreter(0), cbe(0), gcc(0) {}
 
 
 /// ParseInputFile - Given a bytecode or assembly input filename, parse and