Fixes during review of new code

- Mostly indentation fixes
- Added missing test
- Ensure that Item_func_case() checks for stack overruns
- Use real_item() instead of (Item_ref*) item
- Fixed wrong error handling

sql/item_cmpfunc.h

@@ -566,6 +566,7 @@ public:
   longlong val_int();
   String *val_str(String *);
   my_decimal *val_decimal(my_decimal *);
+  bool fix_fields(THD *thd,struct st_table_list *tlist, Item **ref);
   void fix_length_and_dec();
   uint decimal_precision() const;
   table_map not_null_tables() const { return 0; }