Revert "Neon has to be built with OPENSSL_NO_SSL2 define to make it compatible with OpenSSL 1.0.2g."
This reverts commit 955d24d20f1deec6ea68ff7c07bae5c10a69099a.
Revert reason: OpenSSL 1.0.2g actually defines that itself.
Source commit: 87ff292ff44b5e76cd269487c027af05ef5b2106