Allow building MySQL libs against OpenSSL

There are a few long standing issues with MySQL concerning an incompatibility between the embedded YaSSL and the external OpenSSL libraries.

This patch adds a with-openssl option to support building the MySQL libraries against OpenSSL if requsted. This helps the issue by compiling the libraries against OpenSSL, which will connect correctly to an OpenSSL server (the default for RedHat / CentOS).

References:
http://bugs.mysql.com/bug.php?id=40141
http://bugs.mysql.com/bug.php?id=67957