Port installboot as installboot_nbsd and rename the old one.

Also following functionality was added:
- Add install_master to the installboot from NetBSD.
- Check if enough space for bootxx.

Old installboot was renamed to installboot_minix.

boot/installboot/Makefile

@@ -1,6 +1,6 @@
 # installboot: install the boot package; runs on the installer's machine
 
-PROG=	installboot
+PROG=	installboot_minix
 BINDIR=	/usr/bin
 
 SRCS=	installboot.c rawfs.c

boot/updateboot.sh

@@ -24,5 +24,5 @@ echo Installing boot monitor into $BOOT.
 cp $MDEC/boot $BOOT
 
 echo Patching position of $BOOT into $ROOT.
-installboot -d "$ROOT" $MDEC/bootblock $BOOT
+installboot_minix -d "$ROOT" $MDEC/bootblock $BOOT
 sync