Revert "Return a named error in the result object of an expression with no result"

This reverts commit r344647.
This causes build failures with [-Werror, -Wswitch]. Some cases where the newly
introduced enum value is not handled in particular are in:
  lldb/source/Expression/REPL.cpp:350
  lldb/source/Interpreter/CommandInterpreter.cpp:1529
(maybe there could be more)

As I don't understand lldb to make sure the likely trivial fixes are
correct and also as they might need additional tests, leaving to the
author to resolve.

llvm-svn: 344722
diff --git a/lldb/source/Commands/CommandObjectExpression.cpp b/lldb/source/Commands/CommandObjectExpression.cpp
index f6e4007..ac440ef 100644
--- a/lldb/source/Commands/CommandObjectExpression.cpp
+++ b/lldb/source/Commands/CommandObjectExpression.cpp
@@ -487,7 +487,7 @@
         }
       } else {
         if (result_valobj_sp->GetError().GetError() ==
-            lldb::eExpressionProducedNoResult) {
+            UserExpression::kNoResult) {
           if (format != eFormatVoid &&
               m_interpreter.GetDebugger().GetNotifyVoid()) {
             error_stream->PutCString("(void)\n");