bin: Produce output PEM files with text descriptions of their contents.

bin: Produce output PEM files with text descriptions of their contents.

This makes them easier to read.  There's a slight risk of someone being
confused by a malicious file whose text representation doesn't contain
an accurate description of the actual contents, but I think that's a
fairly minor consideration.  The files are also larger than they were
previously, but we'll have to put up with that.