Out of memory error when loading large dataflash logs (>20MB)

Loading a large (50MB) dataflash logs results in an "out of memory" error. 20MB seems to work fine. Don't have anything in between to test!

While this may sound like excessively large logs, EKF really blows out the log size, AND requires detailed log analysis.

https://drive.google.com/file/d/0B9AHb7NB3l6gRVBHUEZTcG1fbWM/edit?usp=sharing

Start by reproducing the failure with the linked 50MB dataflash log and compare it with a working 20MB log. Trace the log-loading path and observe memory usage; done means large EKF-heavy logs load without an out-of-memory error and remain available for detailed analysis.

Written by the indexing model from the issue text.