Portability of Interpolation

[MatthewPeterKelly]

Part of the solution struct includes a function handle for interpolating the solution and the error estimates. This handle sometimes breaks if the solutions is saved and then opened on a different computer.

There might be a simple fix by moving some of the sub-functions to the top level directory of the code. A slightly more challenging (but robust) fix is to replace the interpolation with a data structure that can be read by the matlab command ppval. Then there is no need to pass around function handles.

[MatthewPeterKelly]

I suggest that this issue be fixed by making interp.state and interp.control be matlab pp structs, which can then be evaluated using matlab ppval().