Added a "--debug" option to the "expression" command. 

Cleaned up ClangUserExpression::Evaluate() to have only one variant that takes a "const EvaluateExpressionOptions& options" instead of taking many arguments.

The "--debug" option is designed to allow you to debug your expression by stopping at the first instruction (it enables --ignore-breakpoints=true and --unwind-on-error=false) and allowing you to step through your JIT code. It needs to be more integrated with the thread plan, so I am checking this in so Jim Ingham can make it happen.

llvm-svn: 194009
diff --git a/lldb/source/Commands/CommandObjectExpression.h b/lldb/source/Commands/CommandObjectExpression.h
index a62a212..e0703a2 100644
--- a/lldb/source/Commands/CommandObjectExpression.h
+++ b/lldb/source/Commands/CommandObjectExpression.h
@@ -55,6 +55,7 @@
         bool        ignore_breakpoints;
         bool        show_types;
         bool        show_summary;
+        bool        debug;
         uint32_t    timeout;
         bool        try_all_threads;
         LanguageRuntimeDescriptionDisplayVerbosity m_verbosity;