Fix d3#1935 - the XMLNS namespace is special.

Author: mbostock

d3.js

@@ -631,10 +631,7 @@
     prefix: d3_nsPrefix,
     qualify: function(name) {
       var i = name.indexOf(":"), prefix = name;
-      if (i >= 0) {
-        prefix = name.slice(0, i);
-        name = name.slice(i + 1);
-      }
+      if (i >= 0 && (prefix = name.slice(0, i)) !== "xmlns") name = name.slice(i + 1);
       return d3_nsPrefix.hasOwnProperty(prefix) ? {
         space: d3_nsPrefix[prefix],
         local: name

d3.min.js

@@ -9,14 +9,8 @@ var d3_nsPrefix = {
 d3.ns = {
   prefix: d3_nsPrefix,
   qualify: function(name) {
-    var i = name.indexOf(":"),
-        prefix = name;
-    if (i >= 0) {
-      prefix = name.slice(0, i);
-      name = name.slice(i + 1);
-    }
-    return d3_nsPrefix.hasOwnProperty(prefix)
-        ? {space: d3_nsPrefix[prefix], local: name}
-        : name;
+    var i = name.indexOf(":"), prefix = name;
+    if (i >= 0 && (prefix = name.slice(0, i)) !== "xmlns") name = name.slice(i + 1);
+    return d3_nsPrefix.hasOwnProperty(prefix) ? {space: d3_nsPrefix[prefix], local: name} : name;
   }
 };

src/core/ns.js

@@ -49,6 +49,9 @@ suite.addBatch({
       },
       "names that collide with built-ins are ignored": function(qualify) {
         assert.equal(qualify("hasOwnProperty:test"), "test");
+      },
+      "xmlns-prefixed names use the whole name as the local name": function(qualify) {
+        assert.deepEqual(qualify("xmlns:xlink"), {space: "http://www.w3.org/2000/xmlns/", local: "xmlns:xlink"});
       }
     }
   }