Fixes #526: bad font size separator in tagcloud with some locale

* Force the number format with number_format().
      * Reduce the size deciment number to 2.

tpl/tagcloud.html

@@ -12,8 +12,8 @@
 
     <div id="cloudtag">
         {loop="tags"}
-            <span class="count">{$value.count}</span>
-            <a href="?searchtags={$key|urlencode}" style="font-size:{$value.size}pt;">{$key}</a>
+            <span class="count">{$value.count}</span><a
+                href="?searchtags={$key|urlencode}" style="font-size:{$value.size}em;">{$key}</a>
             {loop="$value.tag_plugin"}
                 {$value}
             {/loop}