An ABI change to libvlccore or libcompat will always be signaled by a
change in a header file. That change will trigger a recompilation and
then relinking of affected plugins.

Thus, there is no need for libvlccore.la and libcompat.la to be
explicit dependencies of plugins. This small hack avoids relinking
every plugin whenever the libvlccore is rebuilt.

modules/control/dbus/dbus.h is removed as it conflicted with the global
libdbus header and was included only once.

If they are really needed, they should be integrated in compat/.
Declaring standard functions static breaks when the target has stubs.