Squeezed bytes and cycles out of the kbhit functions for almost all platforms.

git-svn-id: svn://svn.cc65.org/cc65/trunk@4480 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/plus4/kbhit.s

@@ -1,21 +1,24 @@
 ;
 ; Ullrich von Bassewitz, 06.08.1998
 ;
-; int kbhit (void);
+; unsigned char kbhit (void);
 ;
 
 	.export		_kbhit
-	.import		return0, return1
-	
+
 	.include	"plus4.inc"
 
-_kbhit:
+
+.proc   _kbhit
+
+        ldx     #0              ; High byte of return is always zero
 	lda	KEY_COUNT	; Get number of characters
 	ora	FKEY_COUNT	; Or with number of chars from function keys
-	bne   	L1
-	jmp	return0
-L1:	jmp	return1
-
+        beq     L9
+        lda     #1
+L9:     rts
+
+.endproc