Use po4a to provide translatable documentation

This commit add a new "docs-l10n" make target which uses po4a to:
* create .pot (PO templates) from markdown doc
* update templates and po for enabled languages
* generate translated markdown for completed (> 80%) translations

Currently, no language has been activated.

Signed-off-by: Luca Bruno <lucab@debian.org>

doc/po4a.conf

@@ -0,0 +1,15 @@
+# Add here a list of target languages; po4a will automatically
+# generates .po for them and build .md when translated, eg:
+# [po4a_langs] es fr it pt_BR
+[po4a_langs] 
+[po4a_paths] doc/po/$master.pot $lang:doc/po/$lang/$master.po
+
+# Add here below all source documents to be translated
+[type: text] doc/rust.md $lang:doc/l10n/$lang/rust.md
+[type: text] doc/rustpkg.md $lang:doc/l10n/$lang/rustpkg.md
+[type: text] doc/tutorial-container.md $lang:doc/l10n/$lang/tutorial-container.md
+[type: text] doc/tutorial.md $lang:doc/l10n/$lang/tutorial.md
+[type: text] doc/tutorial-borrowed-ptr.md $lang:doc/l10n/$lang/tutorial-borrowed-ptr.md
+[type: text] doc/tutorial-ffi.md $lang:doc/l10n/$lang/tutorial-ffi.md
+[type: text] doc/tutorial-macros.md $lang:doc/l10n/$lang/tutorial-macros.md
+[type: text] doc/tutorial-tasks.md $lang:doc/l10n/$lang/tutorial-tasks.md

mk/docs.mk

@@ -234,3 +234,8 @@ doc/version_info.html: version_info.html.template $(MKFILE_DEPS) \
 GENERATED += doc/version.md doc/version_info.html
 
 docs: $(DOCS)
+
+docs-l10n:
+	po4a doc/po4a.conf
+
+.PHONY: docs-l10n