Cleanup startup code

I'm starting to understand this stuff better. This makes it possible to
use OS-level interrupts like the keyboard in the code.

system/system.s

@@ -131,13 +131,15 @@ _takeOverSystem:
     OpenLibrary #GraphicsLibrary,#0
     MOVE.L D0,GraphicsBase
 
-    MOVE.L $4,A6
-    CALLLIB _LVOForbid
-
     MOVE.L D0,A6
     MOVE.L gb_ActiView(A6),OldView
     MOVE.L gb_copinit(A6),OldCopper
 
+    MOVE.L #0,A1
+    CALLLIB _LVOLoadView
+    CALLLIB _LVOWaitTOF
+    CALLLIB _LVOWaitTOF
+
     CALLLIB _LVOOwnBlitter
     CALLLIB _LVOWaitBlit
 
@@ -148,17 +150,11 @@ _takeOverSystem:
     PreserveRegister intreq
     PreserveRegister adkcon
 
-    MOVE.L #0,A1
-    CALLLIB _LVOLoadView
-    CALLLIB _LVOWaitTOF
-    CALLLIB _LVOWaitTOF
-
-    LEA _custom,A0
-
     ; http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node0036.html
     MOVE.W #$7FFF,intena(A0) ; disable all interrupts
     ; we need VERTB to use WaitTOF
-    MOVE.W #INTF_SETCLR|INTF_INTEN|INTF_COPER|INTF_VERTB,intena(A0) ; enable master interrupt, copper, and VBR
+    ; PORTS and EXTER give me access to the keyboard and mouse via OS interrupts
+    MOVE.W #INTF_SETCLR|INTF_INTEN|INTF_COPER|INTF_PORTS|INTF_EXTER|INTF_VERTB,intena(A0) ; enable master interrupt, copper, and VBR
 
     MOVE.W #$7FFF,dmacon(a0)
     MOVE.W #DMAF_SETCLR|DMAF_MASTER|DMAF_COPPER|DMAF_RASTER|DMAF_BLITTER|DMAF_SPRITE,dmacon(A0)
@@ -214,9 +210,6 @@ _giveBackSystem:
     CALLLIB _LVOWaitTOF
     CALLLIB _LVOWaitBlit
     CALLLIB _LVODisownBlitter
-
-    MOVE.L $4,A6
-    CALLLIB _LVOPermit
   MOVE.L (SP)+,A6
   RTS