Whilst this isn't as totally flexible as it might be, it's good enough to
remove the todo entry, which was added when -C was forbidden on the #! line.
However, making -C parsing on the #! more flexible probably requires
removing the "feature" that a C<#line 1> directive triggers re-processing
of #! directives.
See also L</"Virtualize operating system access">.
-=head2 -C on the #! line
-
-It should be possible to make -C work correctly if found on the #! line,
-given that all perl command line options are strict ASCII, and -C changes
-only the interpretation of non-ASCII characters, and not for the script file
-handle. To make it work needs some investigation of the ordering of function
-calls during startup, and (by implication) a bit of tweaking of that order.
-
=head2 Organize error messages
Perl's diagnostics (error messages, see L<perldiag>) could use