You can't always use %ld for off_t

Depending on your operating system, off_t may be 32 bits (%ld) or may be
64 bits (%lld).  It's easiest to cast it to a (long long) and just use
%lld in all cases.

See the discussion here:

  http://stackoverflow.com/questions/586928/how-should-i-print-types-like-off-t-and-size-t
Make sysconfdir settable via -D (or #define)

This allows one to set the location of the configuration directory
(by default /etc/fido/mfreq) to another path during compile time.
add support for DESTDIR