Minor tweaks to library

Hi everyone. Yes, I'm still alive. It's just that I have other priorities now than improving the library, and I already feel that the library is in a nice stable state with few enhancements needed.

I've just committed in two minor tweaks:

* I've added a function stub for the Sync API 2.5 method SyncCallDeviceApplication. Thanks to Todd Grigsby for informing me about it

* I've added a DataPos parameter to the OnWriteField event. This lets you know what position the record packer is up to when constructing a record to save to the Palm - I found it invaluable when dealing with complicated records where I needed to manually worry about handling byte alignment.

Paul.