security/libssh2: Update to 1.11.1

* Update MASTER_SITES, use GitHub as primary and upstream main website as fallback
* Fixes CVE-2023-48795
* Convert to CMake for faster builds and cleaner port Makefile
* Make static library option (non default)
* Enable OpenSSL support by default (optional)

PR:		282147
Approved by:	portmgr (maintainer timeout, 2+ weeks)