allow usermodes +n and usermode +I to be auto set from the class block

diff -r 64e4811dd29a include/s_user.h
--- a/include/s_user.h
+++ b/include/s_user.h
@@ -53,6 +53,7 @@
 /* used for parsing user modes */
 #define ALLOWMODES_ANY	0 /**< Allow any user mode */
 #define ALLOWMODES_DEFAULT  1 /**< Only allow the subset of modes that are legit defaults */
+#define ALLOWMODES_AUTO     2 /**< Only allow auto modes */
 
 /* return sets for umode_str() */
 #define UMODE_ALL_PARAMS            0 /**< return the user modes and all parameters */
diff -r 64e4811dd29a ircd/s_user.c
--- a/ircd/s_user.c
+++ b/ircd/s_user.c
@@ -365,7 +365,7 @@
     if (tmpstr) {
       char *umodev[] = { NULL, NULL, NULL, NULL };
       umodev[2] = tmpstr;
-      set_user_mode(cptr, sptr, 3, umodev, ALLOWMODES_ANY);
+      set_user_mode(cptr, sptr, 3, umodev, ALLOWMODES_AUTO);
     }
 
     if (feature_bool(FEAT_AUTOINVISIBLE))
@@ -1355,9 +1355,11 @@
       ClearChannelService(sptr);
     if (!FlagHas(&setflags, FLAG_XTRAOP) && !(IsAnOper(sptr) && HasPriv(sptr, PRIV_XTRA_OPER)))
       ClearXtraOp(sptr);
-    if (!FlagHas(&setflags, FLAG_NOCHAN) && !(IsAnOper(sptr) || feature_bool(FEAT_USER_HIDECHANS)))
+    /* user is an oper, or feature USER_HIDECHANS is TRUE, or the mode is auto set from the class block, else clear mode +n */
+    if (!FlagHas(&setflags, FLAG_NOCHAN) && !(IsAnOper(sptr) || feature_bool(FEAT_USER_HIDECHANS) || allow_modes == ALLOWMODES_AUTO))
       ClearNoChan(sptr);
-    if (!FlagHas(&setflags, FLAG_NOIDLE) && !((IsAnOper(sptr) && HasPriv(sptr, PRIV_NOIDLE)) || feature_bool(FEAT_USER_HIDEIDLETIME)))
+    /* user is an oper with priv NOIDLE, or feature USER_HIDEIDLETIME is TRUE, or the mode is auto set from the class block, else clear mode +I */
+    if (!FlagHas(&setflags, FLAG_NOIDLE) && !((IsAnOper(sptr) && HasPriv(sptr, PRIV_NOIDLE)) || feature_bool(FEAT_USER_HIDEIDLETIME) || allow_modes == ALLOWMODES_AUTO))
       ClearNoIdle(sptr);
     if (!FlagHas(&setflags, FLAG_PARANOID) && !(IsAnOper(sptr) && HasPriv(sptr, PRIV_PARANOID)))
       ClearParanoid(sptr);