Add support for new SoapClient option: keep_alive and ssl_method

[lku]

This PR adds two SoapClient options introduced in PHP 5.4 and 5.5:

keep_alive option allows sending "Connection: close" header directly from SoapClient.

ssl_method option allows to specify the SSL version to use

[Maks3w]

You can remove this. ZF > 2.5 has a minimum of php 5.5

[lku]

@Maks3w Done. I didn't know that master is already for 2.5, thanks!

[lku]

I just accidentally discovered that tests failed in HHVM with this PR. I have to look into that.

[lku]

I played with HHVM little bit and I have no idea how to fix the HHVM errors :( The reason is very simple - there are no SOAP_SSL_METHOD* constants in HHVM (hhvm src vs php src).

Any thoughts? Should I avoid using these constants?

[Maks3w]

define the constants if not defined.

if (!defined('FOO')) {
  define('FOO', 123456789);
}

[Maks3w]

Please rebase your PR. There are merge conflicts.

[lku]

@Maks3w: Rebased and updated my code to short array syntax.

Where should I define these constants? They need to be in global namespace.

[Maks3w]

If constant is not preffixed with \ does not matter if is local or global namespace.

Anyway I think the feature of validate sslMethod can be omitted

[lku]

Ok, I completely removed the SSL method validation.

There are other failures in HHVM, but those were already there. I could take a look at them later.

[weierophinney]

Merged to develop for release with 2.6.0.

[lku]

Thank you 👍

And thank you @Maks3w for your code review