[Xcb] xcb/proto make check failures

[Ran Benita]

I've noticed that `make check` in xcb/proto fails due to schema
validation errors. The following diff fixes the major omissions (not
sure if the diff is entirely correct):

diff --git a/src/xcb.xsd b/src/xcb.xsd
index c1dce3e..3bd0244 100644
--- a/src/xcb.xsd
+++ b/src/xcb.xsd
@@ -44,6 +44,15 @@ authorization from the authors.
     <xsd:complexType>
       <xsd:attribute name="bytes" type="xsd:integer" use="optional" />
       <xsd:attribute name="align" type="xsd:integer" use="optional" />
+      <xsd:attribute name="serialize" type="xsd:boolean" use="optional" />
+    </xsd:complexType>
+  </xsd:element>
+
+  <!-- required start align -->
+  <xsd:element name="required_start_align">
+    <xsd:complexType>
+      <xsd:attribute name="align" type="xsd:integer" use="required" />
+      <xsd:attribute name="offset" type="xsd:integer" use="optional" />
     </xsd:complexType>
   </xsd:element>
 
@@ -198,6 +207,7 @@ authorization from the authors.
   <xsd:group name="fields">
     <xsd:choice>
       <xsd:element ref="pad" />
+      <xsd:element ref="required_start_align" />
       <xsd:element ref="field" />
       <xsd:element ref="list" />
       <xsd:element ref="fd" />

After that, there are still the following errors:

./xinput.xml:177: element case: Schemas validity error : Element 'case': This element is not expected.
./xinput.xml:947: element case: Schemas validity error : Element 'case': This element is not expected.
./xinput.xml:1735: element case: Schemas validity error : Element 'case': This element is not expected.

>From a quick look I can't find the problem, so thought I'd lazily post
it here and let someone else take a look.

Ran