Add TLSv1.1 and TLSv1.2 support

This patch adds TLSv1.1 and TLSv1.2 functionality for encrypted clients and servers. Note that the first OpenSSL version with support for these newer protocols is v1.0.1 and PHP must be built against this version or the new functionality is unavailable.

**New Global Constants:**

- `STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT`
- `STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT`
- `STREAM_CRYPTO_METHOD_TLSv1_1_SERVER`
- `STREAM_CRYPTO_METHOD_TLSv1_2_SERVER`

**New Stream Wrappers:**

- `tlsv1.1://`
- `tlsv1.2://`

**Modified Stream Wrappers:**

The existing `tls://` stream wrapper is now capable of negotiating TLSv1.0, TLSv1.1 or TLSv1.2 connections when built against OpenSSL >= 1.0.1.

Quick Reference on SSL/TLS:

> - SSL v2 is insecure and must not be used.
> - SSL v3 is very old and obsolete. Because it lacks some key features and because virtually all clients
> support TLS 1.0 and better, you should not support SSL v3 unless you have a very good reason.
> - TLS v1.0 is largely still secure; we do not know of major security ﬂaws when they are used for
> protocols other than HTTP. When used with HTTP, it can almost be made secure with careful
> conﬁguration.
> - TLS v1.1 and v1.2 are without known security issues.

-- [*SSL/TLS Deployment Best Practices*](https://www.ssllabs.com/downloads/SSL_TLS_Deployment_Best_Practices_1.3.pdf)

Note that this patch has no BC implications and should be safe to merge with 5.4 and 5.5 branches.