Add css-pseudo-4.vim and test

See also: http://www.w3.org/TR/css-pseudo-4/

test/test.css

@@ -331,6 +331,13 @@
   presentation-level: increment;
 }
 
+.pseudo::selection,
+.pseudo::spelling-error,
+.pseudo::grammer-error,
+.pseuod::placeholder {
+  display: block;
+}
+
 .regions:region {
   flow-into: element;
   flow-from: content;

test/test.html

@@ -340,6 +340,13 @@
         presentation-level: increment;
       }
 
+      .pseudo::selection,
+      .pseudo::spelling-error,
+      .pseudo::grammer-error,
+      .pseuod::placeholder {
+        display: block;
+      }
+
       .regions:region {
         flow-into: element;
         flow-from: content;