pulseaudio: split out libpulse client library

pulseaudio: split out libpulse client library

Move the PulseAudio client libraries into a separate libpulse package,
so a client can depend on just the client library instead of pulling
in the whole daemon. Upstream ships three libraries whose names do not
make the split obvious: libpulse and libpulse-simple are the client
API, libpulsecommon is a private library shared by client and server,
and libpulsecore is the server core used only by the daemon and its
modules. libpulse, libpulse-simple and libpulsecommon go into the new
package; libpulsecore, libpulsedsp and the module helper libraries stay
with pulseaudio-daemon, which now depends on libpulse. The iconv and
gettext users (pulse/utf8.c and pulsecore/i18n.c) are part of
libpulsecommon, so libpulse carries the ICONV_DEPENDS and INTL_DEPENDS
itself.

Enable D-Bus support in both variants, not just the avahi one. D-Bus
support adds the pa_dbus_* and rtkit helpers to libpulsecommon, which
the daemon and its modules link against and which now ships in
libpulse. Since a single libpulse package serves both variants, it has
to be built the same way in both, or the avahi daemon would end up with
a libpulsecommon lacking those symbols. Unconditional D-Bus support is
the simplest way to achieve that; the price is that pure clients now
pull in libdbus.

Two follow-on changes: the D-Bus policy file, previously installed by
the avahi variant only, is now installed by both daemon variants. The
daemon also declares its own libdbus dependency, independent of
libpulse, because libpulsecore links libdbus directly.

Signed-off-by: Mirko Vogt <redacted>