facebook/rocksdb + (-40) -

    folly: LRUCache before this change, with folly enabled (distributed mutex) but on an old compiler (sorry)
    I deleted the original repo for some reason. Sorry for the inconvenience.
    Sorry for the large pull-request, I have broken it down into many small atomic commits though.
    Sorry about this extra PR, as my workflow was messed up when I checked in another work item by accident.
    sorry if these gcc-7/clang-4 cleanups are getting tedious.
    Summary: Ooops, sorry about this.
    Summary: I was pretty sure I compiled this before landing, sorry :/
    I have no idea how I didn't catch this terrible bug when writing a diff, sorry about that :(
    for this diff. Sorry, if I forgot someone or add someone by mistake.
    I came across this while working on column families. CorruptionTest::RecoverWriteError threw a SIGSEG because the descriptor_log_->file() was nullptr. I'm not sure why it doesn't happen in master, but better safe than sorry.
    util/env_posix.cc:68:24: sorry, unimplemented: non-static data member initializers
    util/env_posix.cc:113:24: sorry, unimplemented: non-static data member initializers