feat(generation): Fix CodeGenUtils.emitJavaHeaders

When both classExtended and interfaces are specified for given class space missing between classExtended and implements keyword
---
Index: src/java/com/jogamp/gluegen/CodeGenUtils.java
===================================================================
diff --git a/src/java/com/jogamp/gluegen/CodeGenUtils.java b/src/java/com/jogamp/gluegen/CodeGenUtils.java
--- a/src/java/com/jogamp/gluegen/CodeGenUtils.java	(revision 36f2c2648d6a494865ae1ecd810a6f1241a01ce2)
+++ b/src/java/com/jogamp/gluegen/CodeGenUtils.java	(revision 530107b25986a3ff29a1eda5e028decd4387cf0d)
@@ -130,6 +130,7 @@
             if (classExtended != null) {
                 w.print("extends ");
                 w.print(classExtended);
+                w.print(' ');
             }
         } else {
             if (classExtended != null) {