Update TIdHTTPServer to handle long URIs and long request headers more cleanly

[rlebeau]

If an HTTP client sends either:

• a long request line that exceeds TIdIOHandler.MaxLineLength
• a long header line that exceeds TIdIOHandler.MaxLineLength
• number of headers that exceed TIdHTTPServer.MaximumHeaderLineCount

Then TIdHTTPServer raises an exception and closes the connection. It should send the client back a 414 or 431 response instead of (or at least before) raising the exception.

Also, add new MaximumUriLength and MaximumHeaderLineLength properties.