Only display ACPI bootmenu key if ACPI is present

This patch changes the Forth code for the Beastie menu to only display the
menu option to enable or disable ACPI if the loader detects ACPI.  This avoids
displaying a menu item prompting to enable ACPI if the BIOS doesn't actually
include ACPI.  Any objections?

--- //depot/projects/smpng/sys/boot/forth/beastie.4th	2010-11-08 21:53:18.000000000 0000
+++ //depot/user/jhb/ktrace/boot/forth/beastie.4th	2010-11-08 22:14:04.000000000 0000
_at__at_ -140,12 +140,16 _at__at_
 	fbsdbw-logo
 ;
 
-: acpienabled? ( -- flag )
+: acpipresent? ( -- flag )
 	s" hint.acpi.0.rsdp" getenv
 	dup -1 = if
 		drop false exit
 	then
 	2drop
+	true
+;
+
+: acpienabled? ( -- flag )
 	s" hint.acpi.0.disabled" getenv
 	dup -1 <> if
 		s" 0" compare 0<> if
_at__at_ -178,8 +182,7 _at__at_
 	42 20 2 2 box
 	13 6 at-xy ." Welcome to FreeBSD!"
 	printmenuitem ."  Boot FreeBSD [default]" bootkey !
-	s" arch-i386" environment? if
-		drop
+	acpipresent? if
 		printmenuitem ."  Boot FreeBSD with ACPI " bootacpikey !
 		acpienabled? if
 			." disabled"

-- 
John Baldwin