sadc/sar: New format for binary datafiles (part 1)

sadc/sar: New format for binary datafiles (part 1)

This is the first patch aimed at redesigning sar binary datafiles (see
also issue #135).
This patch changes alignment for some structures, in particular:
long long integers don't need to be aligned on addresses multiple of 16
bytes
only long integers must be aligned on addresses multiple of 8 bytes
so that the size is sufficient for both 32 and 64 bit machines.

The consequence is a binary datafile which is much smaller in size than
its predecessor (on my machine, sa datafiles are now on average 33%
smaller than before).
But of course this new format is no longer compatible with previous one
and as a consequence, older sysstat versions won't be able to read it (I
still plan to update "sadf -c" so that old binary datafiles can be
converted to the up-to-date format).

This patch should also fix issue #148.

Signed-off-by: Sebastien GODARD <sysstat@users.noreply.github.com>