Handle READ_WANT and WRITE_WANT during SSL read operation.

[james-bryant]

Added code to the SSL read function to handle cases where we get an SSL_ERROR_WANT_READ or SSL_ERROR_WANT_WRITE during the operation. In these cases we check the socket with a 5 second timeout to await more data. Then we need to preform the SSL_read again. This issue was discovered while integrating with Microsoft's IIS web server. Fix by James Bryant from Entrust Datacard.