Commit e0508b31 introduced build errors on FreeBSD. This corrects
them.
HAVE_DECL_TIMEZONE should only be used to determine whether or not the
'timezone' variable is defined in a header file or whether it must be
specifically 'extern'ed.
On fbsd, a definition exists, but it is a function in libc and not an
integer timezone value that can be mutliplied or divided.
libcompat and header files will be gone in the upcoming 5.5 release, so we
cannot use the ftime(3) interface there. Fall back to the SVR4 version of the
code, but use the tm_gmtoff field of struct tm to get the timezone.
Unfortunately, that is not portable (because I really really would like to
remove that old and crummy struct timeb from the public API).
