Clean up some mysql stuff to make things work again and

Clean up some mysql stuff to make things work again and
hopefully improve performance a tad.

base/stats/mysql.cc:
    - it's not called sample anymore, it's called tick
    - don't bother to cleanup deleted runs.  Doing this for each run
    is not necessary, it can be done all at once
    - don't query for a bin id every time, just do it once.
    - use locking in a few places to prevent two processes from
    stepping on eachother.
    - don't duplicate subdata ids.  use -1,y and x,-1
base/stats/mysql.hh:
    It's not called sample anymore, it's called tick

--HG--
extra : convert_revision : 95de8498b627c9175da28a66604ec7c719f7804c