Fix SEARCH command in imap4d by replacing the cistrstr typo with cistrcmp. from david

Reference: /n/atom/patch/applied/imap4search
Date: Sat Mar 22 17:53:14 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/upas/imap4d/imap4d.c	Sat Mar 22 17:53:08 2014
+++ /sys/src/cmd/upas/imap4d/imap4d.c	Sat Mar 22 17:53:10 2014
@@ -1162,7 +1162,7 @@
 	if(uids)
 		uid = "UID ";		/* android needs caps */
 	if(rock.next != nil && rock.next->key == SKcharset){
-		if(cistrstr(rock.next->s, "utf-8") != 0
+		if(cistrcmp(rock.next->s, "utf-8") != 0
 		&& cistrcmp(rock.next->s, "us-ascii") != 0){
 			Bprint(&bout, "%s NO [BADCHARSET] (\"US-ASCII\" \"UTF-8\") %s%s failed\r\n", tg, uid, cmd);
 			checkbox(selected, 0);