Make terminal xHEAD and xTAIL registers 32 bits

This enables waiting on them with memory.atomic.wait32 (there is no
wait8) which is needed to avoid spinning when waiting for a key.

prelude.f

@@ -63,18 +63,6 @@
 
 46 EMIT
 
-\ Peripheral register addresses
-
-: TXBUF 0 ;
-: RXBUF 32 ;
-: TXHEAD 64 ;
-: TXTAIL 65 ;
-: RXHEAD 66 ;
-: RXTAIL 67 ;
-: SYSREADY 68 ;
-
-46 EMIT
-
 \ Printing utilities
 
 : CR 10 EMIT ;
@@ -214,6 +202,22 @@ CHAR . EMIT
 
 CHAR . EMIT
 
+\ Peripheral register addresses
+
+HEX
+
+00 CONSTANT TXBUF
+20 CONSTANT RXBUF
+40 CONSTANT TXHEAD
+44 CONSTANT TXTAIL
+48 CONSTANT RXHEAD
+4C CONSTANT RXTAIL
+50 CONSTANT SYSREADY
+
+DECIMAL
+
+46 EMIT
+
 \ A better word-not-found handler
 
 : ANY-RX? RXHEAD AC@ RXTAIL AC@ <> ;