Don't require asciidoctor or a2x, import liberty

.gitmodules

@@ -1,3 +1,6 @@
 [submodule "wuffs-mirror-release-c"]
 	path = wuffs-mirror-release-c
 	url = https://github.com/google/wuffs-mirror-release-c
+[submodule "liberty"]
+	path = liberty
+	url = https://git.janouch.name/p/liberty.git

README.adoc

@@ -38,11 +38,12 @@ a package with the latest development version from Archlinux's AUR.
 
 Building and Running
 --------------------
-Build-only dependencies: Meson, pkg-config, asciidoctor or asciidoc +
-Runtime dependencies: gtk+-3.0, glib>=2.64, pixman-1, shared-mime-info,
-libturbojpeg, libwebp +
+Build-only dependencies:
+ Meson, pkg-config, asciidoctor or asciidoc (recommended but optional) +
+Runtime dependencies:
+ gtk+-3.0, glib>=2.64, pixman-1, shared-mime-info, libturbojpeg, libwebp +
 Optional dependencies: lcms2, LibRaw, librsvg-2.0, xcursor, libheif, libtiff,
-ExifTool, resvg (unstable API, needs to be requested explicitly)
+ ExifTool, resvg (unstable API, needs to be requested explicitly)
 
  $ git clone --recursive https://git.janouch.name/p/fiv.git
  $ meson builddir

liberty

@@ -0,0 +1 @@
+Subproject commit 0e86ffe7c30a4d52eea35856b792567ca1040f56

meson.build

@@ -217,9 +217,11 @@ if not win32
 	asciidoctor = find_program('asciidoctor', required : false)
 	a2x = find_program('a2x', required : false)
 	if not asciidoctor.found() and not a2x.found()
-		error('Neither asciidoctor nor a2x were found')
+		warning('Neither asciidoctor nor a2x were found, ' +
+			'falling back to a substandard manual page generator')
 	endif
 	foreach page : [meson.project_name()]
+		man_capture = false
 		if asciidoctor.found()
 			command = [asciidoctor, '-b', 'manpage',
 				'-a', 'release-version=' + meson.project_version(),
@@ -228,10 +230,16 @@ if not win32
 			command = [a2x, '--doctype', 'manpage', '--format', 'manpage',
 				'-a', 'release-version=' + meson.project_version(),
 				'-D', '@OUTDIR@', '@INPUT@']
+		else
+			command = ['env', 'LC_ALL=C',
+				'asciidoc-release-version=' + meson.project_version(),
+				'awk', '-f', files('liberty/tools/asciiman.awk'), '@INPUT@']
+			man_capture = true
 		endif
 		custom_target('manpage for ' + page,
 			input : 'docs' / page + '.adoc',
 			output : page + '.1',
+			capture : man_capture,
 			command : command,
 			install : true,
 			install_dir : get_option('mandir') / 'man1')