dbus,dbus-test: Move common parts to dbus.inc

dbus and dbus-test share the same source code and base configuration options,
so factor out the common parts into dbus.inc.

This way we can eliminate the need to keep the two recipes in sync. When they
are not properly in sync (e.g. when dbus recipe has extra patches/config
options that are not duplicated in dbus-test) ptest testsuite will actually
test a slightly different codebase. This is due to the fact that dbus-test does
not run the testsuite against the system libdbus library, but instead it
generates a local libdbus.so that needs to configured/compiled as close as
possible to the system one.

(From OE-Core rev: 1cde2935)

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 44ae5d8d6f26fda4ab1a3fef9fc49d74e4ac89f0)
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>