More changes in the Emacs manual

More changes in the Emacs manual

* doc/emacs/fixit.texi (Undo): Mention 'revert-buffer'.
(Fixing Case): Fix punctuation.
(Spelling): Fix a typo.  Suggested by Toon Claes <toon@iotcl.com>
in emacs-manual-bugs@gnu.org.

* doc/emacs/modes.texi (Major Modes): Break a long sentence into
2.  Reported by Stefan Kamphausen <stefan.kamphausen@acrolinx.com>
in emacs-manual-bugs@gnu.org.

* doc/emacs/indent.texi (Just Spaces): Yet another minor
rewording.

* doc/emacs/building.texi (Watch Expressions): Improve wording.
(Multithreaded Debugging): Spell "tool bar" as 2 words.  Reported
by Alberto Sartori <alberto.sartori@sissa.it> in
emacs-manual-bugs@gnu.org.
(Grep Searching): Mention the effect of
'compilation-mode-line-errors'.  (Bug#30397)

* doc/emacs/basic.texi (Moving Point): Minor reformatting and
rewording of what <LEFT> and <RIGHT> do.