Clang++ (and g++) don't define __STDC_VERSION__ which results in
include/spa/support/log.h:101:5: error: '__STDC_VERSION__' is not defined, evaluates to 0 [-Werror,-Wundef]
#if __STDC_VERSION__ >= 199901L
include/pipewire/log.h:64:5: error: '__STDC_VERSION__' is not defined, evaluates to 0 [-Werror,-Wundef]
#if __STDC_VERSION__ >= 199901L
so check if __STDC_VERSION__ is defined before comparing.
Also, include/feature.h additionally defines __USE_ISOC99 (and
__USE_ISOC11 for C11 extension), so check these as well.
Add an interface that can manager a dbus connection.
Make a dbus interface in the core that can create connections running
in the core main loop. Keep this as support for spa plugins.
