spa: add a macro to check for a callback version

spa_interface_call() and friends will quietly do nothing if the version
doesn't match so we need an extra macro to know whether we can
spa_interface_call() for any given version.

This allows us to implement things like:
   if (spa_interface_callback_version_min(1)
        spa_interface_call(..., 1, func_v1)
   else
        spa_interface_call(..., 0, func_v0)