xfce4-dev-tools: update to 4.16.0

Change log:

4.16.0
======
- Bump glib to 2.50 based on xfce4.16 roadmap
- Do not process @LINGUAS@ at xdt-autogen stage
- xfce-build: Add Thunar to container (Fixes #40)
- helpers: Add xfce-build 'pull' argument
- Fail xfce-build container generation if there is any error
- helpers: Prefer xfce-build over xfce-test (Fixes #38)
- helpers: Add new helper xfce-open-gitlab
- Disable CFLAGS override when building CI container
- use strict CFLAGS to catch common mistakes in ci pipeline
- helpers: Add helper to locally run xfce-build
- Add xvfb on xfce-build

4.15.1
======

Various improvements to the helpers introduced in 4.15.0,
cleanup of xdt-autogen code, various fixes for our CI.

- get-translations: Fix line wrapping
- xdt-autogen: Various small improvements
- xdt-autogen: Properly handle whitespaces in filenames
- xdt-autogen: Use sed instead of tr to replace strings
- Updates README.md
- xfce-build: Add libclutter-1.0-dev for xfdashboard build
- Update .gitignore
- helpers: Use blank line for tags message
- helpers: Reuse release notes from NEWS for tag message
- helpers: Simplify xfce-update-news
- helpers: Do not strip NEWS blank line at EOF
- helpers: Install xfce-do-release
- xfce-build: Add depend for mousepad (Fixes #37)
- helpers: Add do-release helper and Readme
- xfce-build: Install python3 version of distutils-extra
- helpers: Make get-translations executable
- get-translations: Remove last comma
- get-translations: Correctly get locale from commit messages
- xfce-build: Replace build-dep with package names

4.15.0
======

- New macro XDT_VERSION_INIT(SEMVER[, TAG])

This macro takes care of setting up the version numbering.
It will define the following macros based on SEMVER and TAG:

   - xdt_version
   - xdt_version_major
   - xdt_version_minor
   - xdt_version_micro
   - xdt_version_tag
   - xdt_version_build
   - xdt_debug_default

If TAG isn't specified, the xdt_version_tag and xdt_version_git
will be empty and xdt_debug_default will be set to "minimum",
otherwise the xdt_version_build will contain a git hash and
xdt_debug_default will be set to "yes"

Example usage:

  XDT_VERSION_INIT([4.15.3],[git])
  AC_INIT([xfce4-someproject], [xdt_version()])
  ...
  XDT_FEATURE_DEBUG([xdt_debug_default])

- XDT_I18N macro will now automatically find the linguas if none are specified during the autoconf run.

- Install m4 macros in default search dir. This makes autoconf find the macros by default.

By setting version via XDT_VERSION_INIT and using XDT_I18N without arguments,
this is no longer necessary to use a separate configure.ac.in and a plain configure.ac can be used.

- Use datarootdir instead of datadir
- xdt-autogen: explicitly set search path for m4 macros
- Install the xfce-helpers
- Add two new helpers to help releasers
- Install m4 macros into default $datadir/aclocal
- Update README for new gitlab urls
- xdt-autogen: Improve and simplify linguas detection
- Let XDT_I18N automatically find the po/*.po as default
- Let configure generate the xdt-autogen script
- Implement XDT_VERSION_INIT
- Add manpage and tests to xdt-csource
- Add xfce4-dev-tools build in addition to container build
- Check BEFORE_SHA along with changes to .po files
- gitlabci: Ensure to run autogen in distcheck stage
- Switch to "foreign" mode for automake
- Add CI templates notes
- Update README with explanation of Dockerfile
- Fix whitespace error
- Add helper script to get all translation-updates
- Integrate xfce-build container build/creation


(gutteridge)