Fix for read-only IMAP folders.

I've come across a problem with a mail server:
Novonyx IMAP4 Server server ready <198d(_dot_)982601609(_at_)home(_dot_)se>

which has a 'security' feature to not allow
read-write access from simultanious session.

Fetchmail assumes it has read-write access and gets
stuck in an endless loop fetching the same message over and over again.
Probably because it cannot flag the message Seen.

Anyway, here's a simple fix for that. :-)

/Santeri Hernejärvi
System Developer, Xpedio
http://xped.io

--- imap.c.orig Mon Feb 19 17:42:48 2001
+++ imap.c      Mon Feb 19 17:52:43 2001
@@ -111,6 +111,18 @@
        }
        else if (strstr(buf, "PREAUTH"))
            preauth = TRUE;
+       /*
+        * The server may decide to make the mailbox read-only, 
+        * which causes fetchmail to go into a endless loop
+        * fetching the same message over and over again. 
+        * 
+        * This checks for the condition and aborts if 
+        * the mailbox is read-only. 
+        *
+        * see RFC 2060 section 6.3.1 (SELECT)
+        */ 
+       else if (strstr(buf, "[READ-ONLY]")) {
+         return PS_ERROR;
     } while
        (tag[0] != '\0' && strncmp(buf, tag, strlen(tag)));