[gtk/matthiasc/for-master] (10 commits) ...Add to the docs README

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  9f4da7d... Merge branch 'matthiasc/for-master' into 'master' (*)
  a2aa25d... build: add gtkoverlaylayout.h to the list of public headers (*)
  7f2e3c4... Merge branch 'carlosgc/fix-build' into 'master' (*)
  25a8fa7... docs: Turn coding style into a markdown document (*)
  6b6c76e... docs: Remove last two steps from the release howto (*)
  e30c974... Add myself to more sections (*)
  c5485cd... Add the beginnings of a docs contribution guide (*)
  347cb94... docs: Link the documentation guidelines (*)
  85af410... Merge branch 'ebassi/howto-docs' into 'master' (*)
  199b00d... Add to the docs README

(*) This commit already existed in another branch; no separate mail sent