doc: adjust txt2tags usage for versions >=3.3

1) drop --css-sugar option from txt2tags as it is no longer supported

Quoting from https://sources.debian.org/src/txt2tags/3.4-2/CHANGELOG.md/,
respectively /usr/share/doc/txt2tags/changelog.gz as present in current
Debian/unstable:

| * Always use CSS sugar and drop `--css-sugar` option (Jendrik Seipp).

2) the xhtml target is also gone since v3.3

Quoting the changelog:

| # Version 3.3 (2019-11-04)
|
| * Update html target to HTML5 and drop xhtml target (Jendrik Seipp).

Also see https://github.com/txt2tags/txt2tags regarding v2.7 vs. v3.x

NOTE: the output of txt2tags v2.6-4.1 (as present in Debian/buster) is
not really useable now. We don't depend on txt2tags >=3.4-2 as present
in Debian/unstable though, as we don't use the HTML build output during
the package build.

diff --git a/doc/Makefile b/doc/Makefile
index c9c2d0c..28a83b8 100644 (file)
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -12,7 +12,7 @@ all: $(MANPAGES) $(HTMLPAGES)
 
 .t2t.html:
        @printf 'TXT2TAGS %s > %s\n' "$<" "$@"
-       @txt2tags --target xhtml --css-sugar --style t2t-modern.css -o- $< \
+       @txt2tags --target html --style t2t-modern.css -o- $< \
 | sed -e '/^$$/d' -e 's/^\\$$//' > $@
 
 clean: