Fixed a ton of gcc compile warnings

Removed some unused variables, added some consts, changed some casts
to const_cast. I don't think any of these changes are very
controversial.

Differential Revision: http://reviews.llvm.org/D9674

llvm-svn: 237218
diff --git a/lldb/source/Interpreter/Options.cpp b/lldb/source/Interpreter/Options.cpp
index a8766f5..50db611 100644
--- a/lldb/source/Interpreter/Options.cpp
+++ b/lldb/source/Interpreter/Options.cpp
@@ -944,7 +944,7 @@
         lldb::CommandArgumentType option_arg_type = opt_defs[opt_defs_index].argument_type;
         if (option_arg_type != eArgTypeNone)
         {
-            CommandObject::ArgumentTableEntry *arg_entry = CommandObject::FindArgumentDataByType (opt_defs[opt_defs_index].argument_type);
+            const CommandObject::ArgumentTableEntry *arg_entry = CommandObject::FindArgumentDataByType (opt_defs[opt_defs_index].argument_type);
             if (arg_entry)
                 completion_mask = arg_entry->completion_type;
         }