Removed joy_masks array.

So far the joy_masks array allowed several joystick drivers for a single target to each have different joy_read return values. However this meant that every call to joy_read implied an additional joy_masks lookup to post-process the return value.

Given that almost all targets only come with a single joystick driver this seems an inappropriate overhead. Therefore now the target header files contain constants matching the return value of the joy_read of the joystick driver(s) on that target.

If there indeed are several joystick drivers for a single target they must agree on a common return value for joy_read. In some cases this was alredy the case as there's a "natural" return value for joy_read. However a few joystick drivers need to be adjusted. This may cause some overhead inside the driver. But that is for sure smaller than the overhead introduced by the joy_masks lookup before.

!!! ToDo !!!

The following three joystick drivers become broken with this commit and need to be adjusted:
- atrmj8.s
- c64-numpad.s
- vic20-stdjoy.s

libsrc/cbm510/joy/cbm510-std.s

@@ -30,17 +30,6 @@
 
         .addr   $0000
 
-; Button state masks (8 values)
-
-        .byte   $01                     ; JOY_UP
-        .byte   $02                     ; JOY_DOWN
-        .byte   $04                     ; JOY_LEFT
-        .byte   $08                     ; JOY_RIGHT
-        .byte   $10                     ; JOY_FIRE
-        .byte   $00                     ; JOY_FIRE2 unavailable
-        .byte   $00                     ; Future expansion
-        .byte   $00                     ; Future expansion
-
 ; Jump table.
 
         .addr   INSTALL
@@ -105,7 +94,7 @@ READ:   ldx     #$0F            ; Switch to the system bank
         lda     (cia2),y        ; Read joystick inputs
         sta     tmp1
 
-; Get the fire bits
+; Get the push button bits
 
         ldy     #CIA::PRA
         lda     (cia2),y
@@ -115,12 +104,12 @@ READ:   ldx     #$0F            ; Switch to the system bank
         cpx     #$00            ; Joystick 0?
         bne     @L1             ; Jump if no
 
-; Joystick 1, fire is in bit 6, direction in bit 0-3
+; Joystick 1, push button is in bit 6, direction in bit 0-3
 
         asl     a
         jmp     @L2
 
-; Joystick 2, fire is in bit 7, direction in bit 5-7
+; Joystick 2, push button is in bit 7, direction in bit 5-7
 
 @L1:    ldx     #$00            ; High byte of return value
         lsr     tmp1
@@ -128,9 +117,9 @@ READ:   ldx     #$0F            ; Switch to the system bank
         lsr     tmp1
         lsr     tmp1
 
-; Mask the relavant bits, get the fire bit
+; Mask the relavant bits, get the push button bit
 
-@L2:    asl     a               ; Fire bit into carry
+@L2:    asl     a               ; push button bit into carry
         lda     tmp1
         and     #$0F
         bcc     @L3