security/pecl-ssh2: Update to 1.0

• Create security/pecl-ssh2-0
• Add UPDATING note

security/pecl-ssh2 (v1.0) --> PHP 7 only.
security/pecl-ssh2-0 (v0.13) --> PHP 5 compatible.

Changes: https://pecl.php.net/package-changelog.php?package=ssh2&release=1.0

PR: 215378
Reported by: Alexander Ushakov <alexander@polyvizor.com>
Approved by: garga (mentor)
Differential Revision: https://reviews.freebsd.org/D10702