atari5200: implement bgcolor() and textcolor()

Includes some other small fixes/cleanups.

libsrc/atari5200/cvline.s

@@ -1 +1,31 @@
-.include "../atari/cvline.s"
+;
+; Ullrich von Bassewitz, 08.08.1998
+;
+; void cvlinexy (unsigned char x, unsigned char y, unsigned char length);
+; void cvline (unsigned char length);
+;
+        .include "atari5200.inc"
+        
+        .export         _cvlinexy, _cvline
+        .import         gotoxy, putchar
+        .importzp       tmp1
+
+_cvlinexy:
+        pha                     ; Save the length
+        jsr     gotoxy          ; Call this one, will pop params
+        pla                     ; Restore the length and run into _cvline
+
+_cvline:
+        cmp     #0              ; Is the length zero?
+        beq     L9              ; Jump if done
+        sta     tmp1
+L1:     lda     COLCRS_5200
+        pha
+        lda     #CH_VLINE       ; Vertical bar
+        jsr     putchar         ; Write, no cursor advance
+        pla
+        sta     COLCRS_5200
+        inc     ROWCRS_5200
+        dec     tmp1
+        bne     L1
+L9:     rts