More changes in the Emacs manuals

More changes in the Emacs manuals

* doc/emacs/custom.texi (Customization Groups, Browsing Custom)
(Custom Themes, Keymaps, Prefix Keymaps, Modifier Keys)
(Function Keys, Named ASCII Chars, Mouse Buttons, Init Examples):
Fix punctuation.  Suggested by Stefan Kamphausen
<stefan.kamphausen@acrolinx.com> in emacs-manual-bugs@gnu.org.

* doc/emacs/basic.texi (Arguments, Repeating): Avoid breaking
commands between lines.  Reported by Wojciech Politarczyk
<w.politarczyk@gmail.com> in emacs-manual-bugs@gnu.org.

* doc/emacs/custom.texi (Init Rebinding): Move index entries about
rebinding keys from "Init File".  (Bug#30528)