Improve and update documentation of search commands
* doc/emacs/search.texi (Lax Search): Renamed from "Search Case";
all references changed. Move the description of lax-whitespace
here. Add description of the new character folding features and
additional customizable options.
(Isearch Yank): Move before "Error in Search".
(Basic Isearch): Improve wording. Add index entries. Add short
description of how to abandon search, making this subsection a
complete introduction to search basics.
(Repeat Isearch): Add index entries. Describe additional
customizable options. Describe mouse clicks.
(Isearch Yank): Add index entries. Describe mouse-2 click in echo
area. Describe more customizable options.
(Error in Isearch): Add index entries.
(Special Isearch): Move actual description of some isearch
commands to other sections, leaving here just the summary of the
commands. Add command that toggles character folding. Describe
commands, like "C-h C-h", that were previously omitted for some
reason.
(Not Exiting Isearch): Describe search-exit-option. Add index
entries.
(Word Search): Describe eww-search-word and eww-search-prefix.
(Symbol Search): Add index entries.
(Regexp Search): Describe regexp-search-ring-max.
(Replacement and Lax Matches): Renamed from "Replacement and
Case"; all references changed. Describe lax-whitespace matching
in replace commands and related options. Describe character
folding in replace commands and related options.
(Query Replace): Describe query-replace-from-to-separator and the
new history features. Add index entries for highlighted text.
Describe query-replace-skip-read-only. Describe more keys
accepted by query-replace.
(Other Repeating Search): More index entries for Occur. Describe
list-matching-lines-default-context-lines.
(Search Customizations): New section, documents customizable
options that were not documented until now.
* doc/emacs/glossary.texi (Glossary): Add "Case Folding" and
"Character Folding".
* etc/NEWS: Move search- and replace-related entries to a single
parent section.