LIBVIRT_ARG_WITH_ALT is more generic than LIBVIRT_ARG_WITH, which
is tailored at switching features on and off.

Rename the macros according to their intended purpose, and add
some documentation to help developers pick between the two.

Usage of AC_REQUIRE will mess with order how LIBVIRT_CHECK_* macros
are composed into configure.ac.  This ensures that the output of
configure --help is properly ordered and grouped into sections.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

Following patch will update LIBVIRT_CHECK_(LIB|LIB_ALT|PKG) macros in
a way that you will be able to call a another macro as a fallback if
the first one fails.  To allow that, we need to move the
LIBVIRT_ARG_WITH out of those macro to not have two or more same lines
in output of "configure --help".
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

Currently, we are checking for sanlock_add_lockspace_timeout
which is good for now. But in a subsequent patch we are going to
use sanlock_write_lockspace (which sets an initial value for io
timeout for sanlock). Now, there is no reason to check for both
functions in sanlock library as the sanlock_write_lockspace was
introduced in 2.7 release and the one we are currently checking
for in the 2.5 release. Therefore it is safe to assume presence
of sanlock_add_lockspace_timeout when sanlock_write_lockspace
is detected.

Moreover, the macro for conditional compilation is renamed to
HAVE_SANLOCK_IO_TIMEOUT (as it now encapsulates two functions).
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

https://bugzilla.redhat.com/show_bug.cgi?id=1251190

So, if domain loses access to storage, sanlock tries to kill it
after some timeout. So far, the default is 80 seconds. But for
some scenarios this might not be enough. We should allow users to
adjust the timeout according to their needs.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>