RFR: JDK-8179557 Update generated Javadoc footer documentation link

[Magnus Ihse Bursie]

Update the JDK Javadoc footer link from [1] to [2].

[1] http://docs.oracle.com/javase/9/docs/index.html

[2] http://www.oracle.com/pls/topic/lookup?ctx=javase9&id=homepage

Bug: https://bugs.openjdk.java.net/browse/JDK-8179557
Patch inline:
diff --git a/make/Javadoc.gmk b/make/Javadoc.gmk
--- a/make/Javadoc.gmk
+++ b/make/Javadoc.gmk
@@ -52,7 +52,7 @@
  DOCROOTPARENT_FLAG ?= TRUE

  # URLs
-JAVADOC_BASE_URL := 
http://docs.oracle.com/javase/$(VERSION_SPECIFICATION)/docs
+JAVADOC_BASE_URL := 
http://www.oracle.com/pls/topic/lookup?ctx=javase9&id=homepage
  BUG_SUBMIT_URL := http://bugreport.java.com/bugreport/
  COPYRIGHT_URL := {@docroot}/../legal/cpyr.html

/Magnus