The full list of functions moved:
int case_stmt_action_expr(LEX *, Item* expr);
int case_stmt_action_when(LEX *, Item *when, bool simple);
int case_stmt_action_then(LEX *);
bool add_select_to_union_list(LEX *,bool is_union_distinct,  bool is_top_level);

This is a preparatory change for "MDEV-10142 PL/SQL parser",
to reuse the code easier between sql_yacc.yy and coming soon sql_yacc_ora.yy.