* dbus/dbus-sysdeps-unix.h: small change to Peter's patch to make
	dbus-sysdeps-unix-util.c build, add unix-specific sysdeps header.

	* dbus/dbus-sysdeps.h, dbus-sysdeps-unix.c: patch from Peter
	Kümmel bug #8249 to make the sysdeps.h read/write/open/close
	functions specifically for sockets only, and move generic
	read/write/open/close into unix-specific code.