cleanup:

* remove unused mysql_option
* don't allocate 5GB of memory in the mtr tests
* restore the behavior in dynamic_column_offset_byte(), put the ifdef correctly
* prefer __attribute__((unused)) to #ifdef
* prefer UNINIT_VAR to LINT_INIT
* make most Warning_info users blissfully unaware of the postponed initialization
* use my_offsetof instead of offsetof where the compiler thinks the latter is incorrect

sql/sql_error.h

@@ -363,7 +363,7 @@ private:
 public:
 
   Warning_info(ulonglong warn_id_arg, bool allow_unlimited_warnings,
-               bool initialize);
+               bool initialize=true);
   ~Warning_info();
 
   /* Allocate memory for structures */