Merged r12310 (#15414).
Merged r12311 (#15427).
Fixed that non-GET API requests respond with 422 (#15427).
Fixed that the sidebar may be displayed empty (#15414).
Use pagination css class for search results pagination (#15398).
HTML5 conformance of error pages (#15381).
Merged r12302 from trunk to 2.4-stable (#15391, #15401)
Fix wiki syntax "bold italic".
Contributed by Karel Pičman.
Merged r12301 from trunk to 2.4-stable (#15391, #15400)
Czech Wiki syntax traslation updated by Karel Pičman.
Merged r12300 from trunk to 2.4-stable (#15395)
German translation updated by Daniel Felix.
Merged r12299 from trunk to 2.4-stable (#15391, #15402)
Czech traslation for 2.4-stable updated by Karel Pičman.
