Remove OPENSSL_instrument_halt and OPENSSL_far_spin, which both might
have been used under DJGPP in the previous century (if at all).
Prefix error messages from mandoc(1) with "mandoc: "
just like almost all other utility programs do.
Suggested by nick@ who wondered where messages came from
when calling mandoc(1) from inside a Perl script.
ok jmc@ nick@