Optimizer: file->`<<() is broken

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=2996

Reported by Robert J. Budzynski, Warsaw University, Dept. of Physics Robert.Budzynski@fuw.edu.pl

Pike v7.3 release 16 running Hilfe v3.1 (Incremental Pike Frontend)
> Stdio.stdout << "FOO!";
invalid digits, cannot convert to mpz
Unknown program: create("FOO!")
HilfeInput:1: ___HilfeWrapper()

in a script it's pretty much the same. Except that it seems often such a statement gets optimized away, and no error appears (no effect, either). To see the error from a script, use the return value -- as in

(Stdio.stdout << "FOO!")->close();