Remove URLStreamHandlerRuntime

* uses reflection to access internal members of the java.net.URL
  class and thus requires modifications to work with JDK 9 EA b148
* has lower performance than ModifiedSystemClassRuntime that is
  used by default and than SystemPropertiesRuntime
* not used by default

org.jacoco.doc/docroot/doc/changes.html

@@ -30,6 +30,8 @@ <h3>API Changes</h3>
 <ul>
   <li><code>JaCoCo.ASM_API_VERSION</code> removed
       (GitHub <a href="https://github.com/jacoco/jacoco/issues/474">#474</a>).</li>
+  <li><code>URLStreamHandlerRuntime</code> removed
+      (GitHub <a href="https://github.com/jacoco/jacoco/issues/471">#471</a>).</li>
 </ul>
 
 <h2>Release 0.7.8 (2016/12/09)</h2>

org.jacoco.doc/docroot/doc/implementation.html

@@ -205,7 +205,9 @@ <h2>Coverage Runtime Dependency</h2>
     classes open a connection on this protocol. The returned connection object
     is the one that provides access to the coverage runtime through its
     <code>equals()</code> method. However to register the protocol the runtime
-    needs to access internal members of the <code>java.net.URL</code> class.</li> 
+    needs to access internal members of the <code>java.net.URL</code> class
+    and thus will require additional modifications to work with JDK 9
+    (at least was required for EA b148), so has been removed in 0.7.9.</li>
   <li><b><code>ModifiedSystemClassRuntime</code></b>: This approach adds a
     public static field to an existing JRE class through instrumentation. Unlike
     the other methods above this is only possible for environments where a Java