documentation updates, dial gcc -g flag up to 11
replay: update remaining etna_vidmem_unlock call in cube_etna2_gc2000 to new API

Commit 2fcaa58c3e0e763c78bb1d28a3d63380f5e65ce2 introduced an additional
(optional) queue parameter to etna_vidmem_unlock. Update the remaining
callsite in cube_etna2_gc2000.