[gtk-doc] (11 commits) ...Merge branch 'wip/documentation' into 'master'

[Stefan Sauer <stefkost src gnome org>]

Summary of changes:

  ee6a899... help/manual: improve autotools setup (*)
  a3e37a3... help/manual: add support for dynamic document version (*)
  d0ae56a... help/manual: add paragraph about history (*)
  9008886... help/manual: small doc cleanups (*)
  665e302... style.css: add bottom spacing for seglistitem (*)
  79de00c... help/manual: consistent use of function element (*)
  093050e... help/manual: fix formatting of program listing (*)
  167053f... style.css: highlight application elements (*)
  ffd5f97... help/manual: install gtk-doc html version of manual (*)
  5999ccf... meson: add support for version.ent (*)
  8b8335c... Merge branch 'wip/documentation' into 'master'

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