More bugs found in OS code

[Adam D. Ruppe]

bearophile wrote:
> Currently this is not caught by D, it prints "12":
> import std.stdio;
> void main() {
>    writefln("%d%d", 1, 2, 3);
> }

That's not really an error. You might change out the format
string at runtime based on user preferences, perhaps for
internationalization, or other reasons.