Add documentation for krb5_error_code

(cherry picked from commit 4d02def)

ticket: 8387
version_fixed: 1.14.2
status: resolved
tags: -pullup

src/include/krb5/krb5.hin

@@ -182,9 +182,15 @@ typedef krb5_int32 krb5_cryptotype;
 typedef krb5_int32      krb5_preauthtype; /* This may change, later on */
 typedef krb5_int32      krb5_flags;
 typedef krb5_int32      krb5_timestamp;
-typedef krb5_int32      krb5_error_code;
 typedef krb5_int32      krb5_deltat;
 
+/**
+ * Used to convey an operation status.  The value 0 indicates success; any
+ * other values are com_err codes.  Use krb5_get_error_message() to obtain a
+ * string describing the error.
+ */
+typedef krb5_int32      krb5_error_code;
+
 typedef krb5_error_code krb5_magic;
 
 typedef struct _krb5_data {