sysstat version 11.5.4 final packaging.
lsm and spec files updated.
CREDITS file updated.
Changelog added.

NOTE: Stable versions (11.2.9 and 11.4.3) also exist and will be
available for download from my web site:

http://pagesperso-orange.fr/sebastien.godard/

The stable versions include only the bug fixes added in sysstat 11.5.4
but not the new features.

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