Starting sysstat 11.1.1

Update sysstat version number in configure script.

Note: 11.1.1 will be a development version, including all the new
features added to sysstat.
Each development version will be associated with a stable version,
including only fixes. So don't worry, there will also actually be a
version 11.0.1, and a version 11.0.2 etc. available for download from my
web site.

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