Binary search in range [ 0L .. count ]. The function is generic in ^T and
 is 'inline' so that the comparison on ^T is optimized.

  - `count` specifies the upper bound for the binary search
  - `valueAt` is a function that returns value ^T at the specified location
  - `value` is the ^T value that we are looking for
  - `lookup` is the lookup semantics as used in Deedle
  - `check` is a function that tests whether we want a given location
    (if no, we scan - this can be used to find the first available value in a series)