Titlebar gradient should not extend the full width

[tpenguinltg]

According to the high-quality screenshots in the GUIdebook gallery, the titlebar gradient should not span the entire width of the titlebar, but only the title portion. The window icon has a solid background (ActiveTitle, InactiveTitle), and the window controls have a solid background (GradientActiveTitle, GradientInactiveTitle).

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If you would like to use it as a reference, I attempted to make a faithful recreation myself a few years ago for a Windows theme creator and I believe I the colour mapping to the various elements are correct. The repo is tpenguinltg/winclassic (demo). You can load the Windows 98 values into the box to see it live.

[jdan]

This is a really nice bit of trivia, thank you :) Will keep this one open to see if anyone wants to throw a PR my way (you're welcome to yourself!)