Although the flex documentation avers that yyalloc and yyrealloc take

Although the flex documentation avers that yyalloc and yyrealloc take
size_t arguments, the emitted scanner actually prototypes them with
type yy_size_t, which is sometimes not the same thing depending on
flex version and platform.  Easiest fix seems to be to use yy_size_t.
Per buildfarm results.