If specific dimensions were specified, use that (like PVR).
Otherwise, try to find the best dimensions.

Previously, the current/default settings were always used.

Also refactor common code with MMAP devices.
In block mode, the read buffer size is controlled. That ensures that
dequeued buffers do not get truncated.

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.