Basically, I wanted to be able to make a dump to a FILE*, and not have

Basically, I wanted to be able to make a dump to a FILE*, and not have
to bother creating a BIO around it.  So here's a few more functions to
make it possible to make the dump using a printing callback, and to
print to a FILE* (based on the callback variant), done in the same
style as the functions in crypto/err/err_prn.c.