Summarize the features in website for next release.

A link has been added to the more detailed changelog which is generated when building the website.
New separate section for Windows downloads in website.
Update the website.

* Add reference to the 64-bit support.
* Remove reference to the installation improvements.
* Other minor changes.
Rebuild the Windows GTK+ bundle.
Improvements for the website.

* Summarize the features for current release.
* Add some information about the 64-bit Windows version.
Show build number in about dialog.
Improvements to the version-information resource in Windows build.

* Add build number to the installer.
* Add bitness to the main executable and DLLs.
* Other minor changes.
Update the WinSparkle configuration.