* Add separate directories for the individual netboot ROMs and
always build them.
* Each bootloader Makefile explicitly specifies the start file
and link address it wishes to use.
* genprom becomes a proper host program.
* Make sure all generated files get cleaned up.
* Set BINDIR in Makefile.inc
* Add compressed image support to pxeboot.
* Make pxeboot use the default serial console speed (9600).