[ticket/13934] Add enctype clause for profile fields

Adds a template variable (the same) in all places where profile fields
may need an enctype clause in the corresponding forms.

PHPBB3-13934

phpBB/styles/prosilver/template/ucp_register.html

@@ -14,7 +14,7 @@
 // ]]>
 </script>
 
-<form method="post" action="{S_UCP_ACTION}" id="register">
+<form id="register" method="post" action="{S_UCP_ACTION}"{S_FORM_ENCTYPE}>
 
 <div class="panel">
 	<div class="inner">