linux system (namely mine) chokes on our definitions and uses of the "HZ"
symbol in crypto/tmdiff.[ch] and apps/speed.c as a "bad function cast"
(when in fact there is no function casting involved at all). In both cases,
it is easily worked around by not defining a cast into the macro and
jiggling the expressions slightly.

In addition - this highlights some cruft in openssl that needs sorting out.
The tmdiff.h header is exported as part of the openssl API despite the fact
that it is ugly as the driven sludge and not used anywhere in the library,
applications, or utilities. More weird still, almost identical code exists
in apps/speed.c though it looks to be slightly tweaked - so either tmdiff
should be updated and used by speed.c, or it should be dumped because it's
obviously not useful enough.

Rather than removing it for now, I've changed the API for tmdiff to at
least make sense. This involves taking the object type (MS_TM) from the
implementation and using it in the header rather than using "char *" in the
API and casting mercilessly in the code (ugh). If someone doesn't like
"MS_TM" and the "ms_time_***" naming, by all means change it. This should
be a harmless improvement, because the existing API is clearly not very
useful (eg. we reimplement it rather than using it in our own utils).

However, someone still needs to take a hack at consolidating speed.c and
tmdiff.[ch] somehow.