cmdparse: add function to convert error status to string

This is used to avoid duplication of error printing in chronyd and
chronyc.

cmdparse.h

@@ -59,6 +59,9 @@ typedef struct {
 /* Parse a command to add an NTP server or peer */
 extern CPS_Status CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src);
   
+/* Get a string describing error status */
+extern void CPS_StatusToString(CPS_Status status, char *dest, int len);
+
 /* Remove extra white-space and comments */
 extern void CPS_NormalizeLine(char *line);