Bugfix PHP 7 support

[liborm85]

PR fixed and improved the following:

• bugfix handling in ssh2.sftp wrapper with multiple connections (Bug: https://bugs.php.net/bug.php?id=72988)
• remove obsolete code for PHP 7 and remove compatibility with older PHP versions (4.x and 5.x)
• fix raising warning in ssh2_poll
• fix raising erros in ssh2_scp_send
• fix returning values in parse path wrapper function

I do not know how fix TODOs with zend_list_addref and zend_list_delete, but all works correctly without fixing this.

[weltling]

Thanks for the PR! It would make sense you to split it into smaller parts by the actual topic. Particularly, the most important thing here is the bugfix for #72988, so it should be the first thing. All the white space change and other amount of change have nothing to do with it.

Also, PHP 5 part will still need this fix. The PHP 5 support is also required for the next couple of years, for sure. But anyway, it's discussable later. IMHO every grouped change should sit in a separate PR, otherwise it is quite impossible to evaluate the impacts.

Thanks.

[liborm85]

@weltling Ok, i splitted to few PRs, resolves what was broken attempting to implement in PHP 7.

I thought that the support for PHP 5 should be only a branch php5, because the master is only for PHP 7. Many support has been removed earlier in the master. Ok, PRs for removing compatibility with PHP 5 I will not do.

[weltling]

@liborm85 thanks! With PHP5 what i meant - it needs to be supported along with 7, and patches will need to be backported. As I see you wrote in #15, the patch is only relevant for 7, so it is fine then. The master branch is does not support PHP 5 already, so the cleanup can be done with a separate PR as well.

I'm going to check your split PRs in the next days, if no one beats me to it.

Cheers