add switch to disable revocation checks in libcurl

[faky1337]

Will disable revocation checks if started with -nosslrevocation. Handy for some people who have issues with revocation checks in Windows Schannel. #182 The cause for the issue is really not known and nobody was able to figure out what the issue might be. This would be a workaround that people could add to their startup txt.

As far as I understand, the checks just try to look up if an issued certificate was revoked later. When removing the CA for northstar.tf I was still not able to connect so it will surely not disable the entire certificate checks.