Completed run_code_and_set_string_to_coproce...().

Completed run_code_and_set_string_to_coprocess_output_from_redirection(). Yes,
that's right: the most ungodly brutal function this side of an obfuscated Perl
contest actually seems to be behaving reliably. For once. (And probably never
again. But let us mildly gloat whilst we may... May we?)