Really fix linker issue with "debuginfo" variable.

The 16bit and 32bit code can't share debuginfo because it points to
    code and must point to 16bit code in 16bit mode.  Introduce two
    separate variables - one for 32bit mode and one for 16bit mode.
diff --git a/src/output.c b/src/output.c
index b5b7d52..ab2236b 100644
--- a/src/output.c
+++ b/src/output.c
@@ -84,7 +84,11 @@
     debug_serial(c);
 }
 
-struct putcinfo debuginfo VAR16VISIBLE = { putc_debug };
+#if MODE16
+static struct putcinfo debuginfo VAR16 = { putc_debug };
+#else
+static struct putcinfo debuginfo = { putc_debug };
+#endif
 
 
 /****************************************************************