Merge branch 'jk/asciidoc-markup-fix' into maint

Various documentation mark-up fixes to make the output more consistent in general and also make AsciiDoctor (an alternative formatter) happier. * jk/asciidoc-markup-fix: doc: convert AsciiDoc {?foo} to ifdef::foo[] doc: put example URLs and emails inside literal backticks doc: drop backslash quoting of some curly braces doc: convert \--option to --option doc/add: reformat `--edit` option doc: fix length of underlined section-title doc: fix hanging "+"-continuation doc: fix unquoted use of "{type}" doc: fix misrendering due to `single quote'