Remove unnecessary casts to uchar. The casts are stemming from

the lexer API which internally uses  unsigned char variables to
address its state map. The implementation of the lexer should be
internal to the lexer, and not influence the rest of the code.

sql/event_data_objects.h

@@ -217,7 +217,7 @@ public:
   */
   bool do_not_create;
 
-  const uchar *body_begin;
+  const char *body_begin;
 
   LEX_STRING dbname;
   LEX_STRING name;