Ensure that the first code executed is our decryption routine

This pull-request closes #37, by making sure the first code we
run in our binary is our decryption code (if that is enabled).

Previously we ran some code:

        call foo
        [decrypt code]
        [start of encrypted code]
        foo:
        [end of encrypted code]

If we called a routine that was after the decryption code we'd
be running gibberish.  This seemed to work by accident in some
systems, but was obviously broken.

game.z80

@@ -143,9 +143,6 @@ MACRO POP_ALL
         ;
         ORG ENTRYPOINT
 
-        ; Call system-specific setup routine before we do anything else.
-        call bios_init
-
         ;
         ; Our game can be compiled with optional "encryption", which uses
         ; a simple scheme to hide the strings in our binary.
@@ -181,6 +178,10 @@ enc_loop:
 enc_end:
 ENDIF
 
+        ; Call system-specific setup routine before we do anything else.
+        call bios_init
+
+
         ; Here we're going to copy our game-state to the end of RAM
         ;
         ; We do this so that everything "resets" if the player dies/wins