Maria: first version of checkpoint (WL#3071), least-recently-dirtied page flushing (WL#3261), recovery (WL#3072),
control file (WL#3234), to serve as a detailed LLD. It looks like C code, but does not compile (no point in making it compile,
as other modules on which I depend are not yet fully speficied or written); some pieces are not coded and just marked in comments.
Files' organization (names, directories of C files) does not matter at this point.
I don't think I had to commit so early, but it feels good to publish something, gives me the impression of moving forward :)


storage/maria/checkpoint.c:
  WL#3071 Maria checkpoint, implementation
storage/maria/checkpoint.h:
  WL#3071 Maria checkpoint, interface
storage/maria/control_file.c:
  WL#3234 Maria control file, implementation
storage/maria/control_file.h:
  WL#3234 Maria control file, interface
storage/maria/least_recently_dirtied.c:
  WL#3261 Maria background flushing of least-recently-dirtied pages, implementation
storage/maria/least_recently_dirtied.h:
  WL#3261 Maria background flushing of least-recently-dirtied pages, interface
storage/maria/recovery.c:
  WL#3072 Maria recovery, implementation
storage/maria/recovery.h:
  WL#3072 Maria recovery, interface