3.4.0 (stable)

* Add track_object(), deprecate track_obj()
  (Kjell Ahlstedt) Issue #78 (LordVolumeForm)
* Add trackable_signal_with_accumulator and trackable_signal
  (Kjell Ahlstedt) Issue #80 (H2NCH2COOH)

Examples, tests:
* examples/member_method: Make on_print() non-virtual
* test_accumulated.cc: clang++ requires another 'template'
  (Kjell Ahlstedt)
* test_limit_reference.cc: Don't use auto where a slot is required
  (Kjell Ahlstedt) Issue #44 (Murray Cumming)

Documentation:
* signal::make_slot(): Note that signal does not derive from trackable
  (Kjell Ahlstedt) Issue #80 (H2NCH2COOH)

Build:
* Meson: Avoid configuration warnings
  (Kjell Ahlstedt)
* Meson, MSVC: Compensate for the lack of msvc_recommended_pragmas.h
  (Chun-wei Fan)
* Fix build with -Dbuild-deprecated-api=false
  (Kjell Ahlstedt) Issue #82 (bbhtt)
* Meson: Detect if we build from a git subtree
  (William Roy) Merge request gtkmm!72
* Meson: Simplify lookup of python command
  (wael444) Pull request #83
* Meson: Add build_tests option
  (Fabrice Fontaine) Pull request #84