Feature request: Add timeout and retry parameters for curl_easy_perform

[stweil]

A batch of more than 40000 tesseract runs with images from the net randomly hangs in curl_easy_perform. Maybe this is caused by problems of the server which delivers the images.

By default the processes which have that problem will hang without a time limit.

Adding a new parameter could allow a user configurable timeout. See https://curl.se/libcurl/c/CURLOPT_TIMEOUT.html for details.

Another parameter could specify how often tesseract should retry the image download.