Changes

contrib/windows: fix the msvc lib soname
It should be 15 instead of 12 to match what we use on Unix.
Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>

windows: add a test to verify that MSVC version/soname match the
official numbers
MSVC hardwires the VERSION numbers/strings and soname in its manually
generated
*_config.h files and in the vcxproj files. Make sure they match what we
have in normal headers and VERSION files.
Only check the soname when in a release branch (ignore on master, where
the lib version is 0:0:0).
This test doesn't run automatically in make check because it requires
bash and grep supporting -P. There's no need to run it for each build
on each slave anyway. So just run it manually in the main jenkins job.
Signed-off-by: Valentin Hoyet <Valentin.Hoyet@inria.fr> Signed-off-by:
Brice Goglin <Brice.Goglin@inria.fr>