Make the Expression Execution result enum available to the SB API layer.

Add a callback that will allow an expression to be cancelled between the
expression evaluation stages (for the ClangUserExpressions.)

<rdar://problem/16790467>, <rdar://problem/16573440>

llvm-svn: 207944

lldb/source/Commands/CommandObjectThread.cpp

@@ -1503,7 +1503,7 @@ protected:
             options.SetUnwindOnError(true);
             options.SetUseDynamic(eNoDynamicValues);
             
-            ExecutionResults exe_results = eExecutionSetupError;
+            ExpressionResults exe_results = eExecutionSetupError;
             exe_results = target->EvaluateExpression (command,
                                                       frame_sp.get(),
                                                       return_valobj_sp,