Docs/WordPress.WhiteSpace.CastStructureSpacing (#1738)

Adds documentation for the WordPress.WhiteSpace.CastStructureSpacing

Related to #1722

Author: ckanitz

WordPress/Docs/WhiteSpace/CastStructureSpacingStandard.xml

@@ -0,0 +1,19 @@
+<documentation title="Cast Structure Spacing">
+    <standard>
+    <![CDATA[
+    A type cast should be preceded by whitespace.
+    ]]>
+    </standard>
+    <code_comparison>
+        <code title="Valid: space before typecast.">
+        <![CDATA[
+$a =<em> </em>(int) '420';
+        ]]>
+        </code>
+        <code title="Invalid: no space before typecast.">
+        <![CDATA[
+$a <em>=(</em>int) '420';
+        ]]>
+        </code>
+    </code_comparison>
+</documentation>