add wget md5 return case func, add ask user func, ask user to issue wget...

... no check ssl if gpg url has invalid or expired cert. Fix format and typo in usage. Not fully tested, need came from trying apt-cyg on clean installs of cygwin, sourceware currently has an invalid ssl according to wgets strict checking. I had problems deleting existing gnupg keys, and didn't have time to look into it further.