2.50.2 (stable):

* Fontset: Use callback functions with C linkage
  (Kjell Ahlstedt) Issue glibmm#1 (Murray Cumming)
* Coverage: Don't use deprecated pango_coverage_ref/unref()
  (Kjell Ahlstedt)

Documentation:
* Doxyfile.in: Don't hide undocumented classes
  (Kjell Ahlstedt)
* README.win32: Convert to MarkDown and rename to README.win32.md
  Make dependencies clearer
  (Chun-wei Fan)
* Remove AUTHORS, HACKING, README.SUN; add general info to README.md
  (Kjell Ahlstedt) Issue gtkmm#140

Meson build:
* Detect if we build from a git subtree
  (William Roy) Merge request gtkmm!72
* Don't copy files with configure_file()
  (Kjell Ahlstedt)
* Fix the evaluation of is_git_build on Windows
  (Kjell Ahlstedt) Issue gtkmm#131 (William Roy)
* Don't fail if warning_level=everything
  (Daniel Boles, Kjell Ahlstedt) Merge request gtkmm!87