Fix some Texinfo markup in manuals

Fix some Texinfo markup in manuals

* doc/emacs/macos.texi (Mac / GNUstep Customization):
* doc/lispintro/emacs-lisp-intro.texi (condition-case):
* doc/lispref/control.texi (pcase Macro):
* doc/lispref/debugging.texi (Internals of Debugger):
* doc/lispref/internals.texi (Building Emacs):
* doc/lispref/modes.texi (Imenu):
(Parser-based Font Lock, Parser-based Indentation):
* doc/lispref/parsing.texi (Retrieving Nodes, Tree-sitter C API):
* doc/lispref/processes.texi (Network, Bindat Types):
* doc/lispref/searching.texi (Rx Functions):
* doc/lispref/text.texi (Replacing):
* doc/lispref/windows.texi (Textual Scrolling):
* doc/misc/calc.texi (Killing From Stack, Customizing Calc):
* doc/misc/cc-mode.texi (Misc Font Locking, List Line-Up):
* doc/misc/ede.texi (ede-cpp-root-project)
(ede-proj-target-makefile, ede-sourcecode):
* doc/misc/ert.texi (Running Tests in Batch Mode):
* doc/misc/eudc.texi (Emacs-only Configuration, The Server Hotlist):
* doc/misc/eww.texi (Advanced):
* doc/misc/flymake.texi (Starting Flymake)
(Proc customization variables):
* doc/misc/tramp.texi (File name completion):
* doc/misc/gnus.texi (Summary Buffer Lines, Gnus Registry Setup)
(Fancy splitting to parent, Customizing the IMAP Connection)
(Mail Source Specifiers, Agent as Cache): Consistently mark up nil
and t as @code.  Also fix the markup and wording of some surrounding
text (bug#64016).

* doc/lispref/display.texi (SVG Images, Icons):
* doc/lispref/modes.texi (Customizing Keywords): Prefer ASCII
apostrophe over Unicode right single quotation mark.