settable codepage() on RP6502

include/rp6502.h

@@ -121,7 +121,7 @@ int __cdecl__ xregn (char device, char channel, unsigned char address, unsigned
     ...);
 int __cdecl__ xreg (char device, char channel, unsigned char address, ...);
 int phi2 (void);
-int codepage (void);
+int codepage (int);
 long lrand (void);
 int __fastcall__ stdin_opt (unsigned long ctrl_bits, unsigned char str_length);
 int __fastcall__ read_xstack (void* buf, unsigned count, int fildes);

libsrc/rp6502/codepage.c

@@ -1,6 +1,7 @@
 #include <rp6502.h>
 
-int __fastcall__ codepage (void)
+int __fastcall__ codepage (int cp)
 {
+    ria_set_ax (cp);
     return ria_call_int (RIA_OP_CODEPAGE);
 }