Merge remote-tracking branch 'origin/1.9' into 1.10

src/box/box.cc

src/box/box.h

src/box/lua/cfg.cc

src/box/lua/load_cfg.lua

src/box/vinyl.c

src/box/vinyl.h

src/box/vy_cache.c

src/box/vy_cache.h

test/unit/vy_iterators_helper.c

test/unit/vy_point_lookup.c

test/vinyl/cache.result

test/vinyl/cache.test.lua