* dbus/dbus-glib-error-enum.h: autogenerate the GError enum
codes from the dbus error names
* glib/dbus-glib.h: move to subdir dbus/ since it's included
as dbus/dbus-glib.h and that breakage is now visible due to
including dbus/dbus-glib.h in dbus-glib-lowlevel.h
* glib/dbus-glib.h: s/gproxy/g_proxy/
* dbus/dbus-shared.h: new header to hold stuff shared with
binding APIs
* dbus/dbus-protocol.h (DBUS_ERROR_*): move errors here rather
than dbus-errors.h
* glib/dbus-glib.h (dbus_set_g_error): move to
dbus-glib-lowlevel.h
* glib/dbus-glib.h: remove dbus/dbus.h from here; change a bunch
of stuff to enable this
* dbus/dbus-glib-lowlevel.h: put dbus/dbus.h here
* a bunch of other changes with the same basic "separate glib
bindings from dbus.h" theme
