Use -y (instead of -o) for overwrite (rz compatible).

Added support for -o to disable Zmodem CRC-32 mode (rz compatible).
Added supprot for rx -c (rz/rb/rx compatible).

src/sbbs3/sexyz.c

@@ -1225,7 +1225,8 @@ static const char* usage=
 	"socket = TCP socket descriptor\n"
 #endif
 	"\n"
-	"opts   = -o  to overwrite files when receiving\n"
+	"opts   = -y  to overwrite files when receiving\n"
+	"         -o  disable Zmodem CRC-32 mode (use CRC-16)\n"
 	"         -s  disable Zmodem streaming (Slow Zmodem)\n"
 	"         -4  transmit with 4K Zmodem blocks\n"
 	"         -8  transmit with 8K Zmodem blocks (ZedZap)\n"
@@ -1332,6 +1333,7 @@ int main(int argc, char **argv)
 	zm.block_size			=iniReadInteger(fp,"Zmodem","BlockSize",zm.block_size);		/* 1024 or 8192 */
 	zm.max_errors			=iniReadInteger(fp,"Zmodem","MaxErrors",zm.max_errors);
 	zm.escape_telnet_iac	=iniReadBool(fp,"Zmodem","EscapeTelnetIAC",TRUE);
+	zm.want_fcs_16			=iniReadBool(fp,"Zmodem","CRC16",FALSE);
 
 	if(fp!=NULL)
 		fclose(fp);
@@ -1432,19 +1434,25 @@ int main(int argc, char **argv)
 					case 'K':	/* sz/rz compatible */
 						xm.block_size=1024;
 						break;
+					case 'C':	/* sz/rz compatible */
+						mode|=CRC;
+						break;
 					case '4':
 						zm.block_size=4096;
 						break;
 					case '8':
 						zm.block_size=8192;
 						break;
+					case 'O':	/* disable Zmodem CRC-32 */
+						zm.want_fcs_16=TRUE;
+						break;
 					case 'S':	/* disable Zmodem streaming */
 						zm.no_streaming=TRUE;
 						break;
 					case 'G':	/* Ymodem-G */
 						mode|=GMODE;
 						break;
-					case 'O':
+					case 'Y':
 						mode|=OVERWRITE;
 						break;
 					case '!':