Parser: remove several uses of `syntax_error()` by explicitly using `no_override_flag` instead of `override_flag` when this flag is disallowed. A conflict is avoided by decorating `override_flag` with `%inline`.
Parser: remove several uses of `syntax_error()` by explicitly using
`no_override_flag` instead of `override_flag` when this flag is disallowed.
A conflict is avoided by decorating `override_flag` with `%inline`.

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml