Refactoring of a lot of code.

This commit introduces a lot of changes such as:
  * Types to handle need to be whitelisted by adding them in the
    whitelist.txt file.
  * Providing a way to override the name of a class.
  * Providing a way to override GIR data with .defs data located in
    src/overriders.
  * Adding methods to Block and DefsFile classes to get information
    from a Block (fields) and add them in an existing DefsFile.
  * Factorizing the IntrospectionParser code.
  * Add utf8 and filename types as registered String types.
  * Removing .defs files that we needed before.

There are still some known issues such as public API not matching the
generated and errors throwing not handle yet.

src/bindings/org/gnome/glib/File.java

@@ -38,7 +38,10 @@
  * @author Guillaume Mazoyer
  * @since 4.1.2
  */
-final class File extends Object
+/*
+ * FIXME: this should not be public.
+ */
+public final class File extends Object
 {
     private File(long pointer) {
         super(pointer);

src/bindings/org/gnome/gtk/Notebook.java

@@ -214,7 +214,7 @@ private SwitchPageHandler(SwitchPage handler) {
             this.handler = handler;
         }
 
-        public void onSwitchPage(Notebook source, long page, int pageNum) {
+        public void onSwitchPage(Notebook source, Widget page, int pageNum) {
             handler.onSwitchPage(source, pageNum);
         }
     }