FR: Better network error reporting to reduce support headaches

When using network functions in JUCE there’s no useful error reporting.

You can’t tell the difference between a server not responding, an SSL configuration error, a DNS error or a rejected connection.

If WebInputStream::isError() and the various URL functions that also make connections (e.g. readEntireXmlStream), could be augmented by something that returned the most complete information available about the error codes from the operating system, many hours of support time could be saved!