* Deal with the new flex 2.5.31 as follows:

   * Deal with the new flex 2.5.31 as follows:
     - Add main and yywrap functions, though they were not needed before.
     - Call yyunput instead of unput macro, as the macro uses yytext_ptr,
       which flex undefes before the bottom set of functions are defined.
     Closes: #189040
   * Various other fixes to build without warnings.