Limit PM max length

We encrypt PMs, so if the encrypted text is truncated by mysql, the
entire message is destroyed. Truncate it before encryption so that
doesn't happen

classes/misc.class.php

     $UnescapedSubject = $Subject;
     $UnescapedBody = $Body;
     $Subject = db_string($Subject);
-    $Body = DBCrypt::encrypt($Body);
+    $Body = DBCrypt::encrypt(substr($Body, 0, 49135)); // 49135 -> encryption -> 65536 (max length in mysql)
     if ($ToID == 0) {
       // Don't allow users to send messages to the system
       return;

sections/inbox/compose.php

         <h3>Subject</h3>
         <input type="text" class="required" name="subject" size="95" value="<?=(!empty($Subject) ? $Subject : '')?>" /><br />
         <h3>Body</h3>
-        <textarea id="body" class="required" name="body" cols="95" rows="10" onkeyup="resize('body')"><?=(!empty($Body) ? $Body : '')?></textarea>
+        <textarea id="body" class="required" name="body" cols="95" rows="10" maxlength="49000" onkeyup="resize('body')"><?=(!empty($Body) ? $Body : '')?></textarea>
       </div>
       <div id="preview" class="hidden"></div>
       <div id="buttons" class="center">