when the text in the description field is larger than 500 kB, DAVx5 stops the synchronization process

[SergeyPetrov98]

When the text in the description field is larger than 500 kB, DAVx5 stops the synchronization process.

Older versions of DAVx5 threw an exception (see logcat_davx.txt), but the new version (4.4.3.2) silently stops the synchronization on the current event, and consequently all the events past the current doesn't get to the device. The synchronization stop was noticed, when DAVx5 processed letters containing a mix of simple and base64 text in the description field.

I have made a patch (davx.patch), which does the following:

1. it substitutes all the base64 text with the message: "--- the message was cut by DAVx5 ---";
2. if the message is anyway larger than 500 kB, it substitutes the text past 500 kB with the message: "--- the message was cut by DAVx5 ---".

May I propose this to be pushed into the master?