fix CHARSET(UUID())

sql/item_strfunc.cc

@@ -2730,6 +2730,7 @@ String *Item_func_uuid::val_str(String *str)
 
   str->realloc(UUID_LENGTH+1);
   str->length(UUID_LENGTH);
+  str->set_charset(system_charset_info);
   s=(char *) str->ptr();
   s[8]=s[13]='-';
   tohex(s, time_low, 8);

sql/item_strfunc.h

@@ -696,7 +696,10 @@ class Item_func_uuid: public Item_str_func
 {
 public:
   Item_func_uuid(): Item_str_func() {}
-  void fix_length_and_dec() {max_length= UUID_LENGTH; }
+  void fix_length_and_dec() {
+    collation.set(system_charset_info);
+    max_length= UUID_LENGTH;
+  }
   const char *func_name() const{ return "uuid"; }
   String *val_str(String *);
 };