(fancy-startup-text): Renamed from fancy-splash-text.

(fancy-startup-text): Renamed from fancy-splash-text.
Several items removed, simplified, or put on one line.
(fancy-about-text): Add substantial contents, part of startup text.
(fancy-splash-head): Make "GNU" or "GNU/Linux" a link.
(normal-splash-screen): Call normal-mouse-startup-screen,
normal-no-mouse-startup-screen, or normal-about-screen.
(normal-mouse-startup-screen): New fn, broken out, shortened.
(normal-no-mouse-startup-screen): New fn, broken out.
(normal-about-screen): New function, contents all new.