Merge branch 'jx/l10n-workflow-change'

A workflow change for translators are being proposed. * jx/l10n-workflow-change: l10n: Document the new l10n workflow Makefile: add "po-init" rule to initialize po/XX.po Makefile: add "po-update" rule to update po/XX.po po/git.pot: don't check in result of "make pot" po/git.pot: this is now a generated file Makefile: remove duplicate and unwanted files in FOUND_SOURCE_FILES i18n CI: stop allowing non-ASCII source messages in po/git.pot Makefile: have "make pot" not "reset --hard" Makefile: generate "po/git.pot" from stable LOCALIZED_C Makefile: sort source files before feeding to xgettext