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

Reference: /n/sources/patch/applied/imap4d-cistrcmp
Date: Mon Aug 26 23:11:28 CES 2013
Signed-off-by: djc@9grid.fr

--- /sys/src/cmd/ip/imap4d/imap4d.c	Mon Aug 26 23:11:04 2013
+++ /sys/src/cmd/ip/imap4d/imap4d.c	Mon Aug 26 23:10:52 2013
@@ -1074,7 +1074,7 @@
 	if(uids)
 		uid = "uid ";
 	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);