wxCurlHTTP::Get will block indefinately

[iwbnwif]

A Get transfer using wxCurlHTTP will block indefinitely because it is impossible to set a timeout.

The root cause is that each ::Get call calls wxCurlBase::SetCurlHandleToDefaults(), which resets all curl options.

The solution is to call SetCurlHandleToDefaults() only on setup, but also to provide a similar public function in case a user desires to reset options between successive ::Get() calls.