This patch fixes clean in case of missing directories and
also adds code to distclean that removes the following files:
 qemu-monitor.texi roms/seabios/config.mak roms/vgabios/config.mak

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>