- add `libssh2:libssh2` target that selects the shared lib if built,
otherwise the static one.
- re-add `Libssh2:libssh2` target for compatibility with v1.10.0 and
earlier. This is an alias for `libssh2:libssh2`.
- keep `libssh2:libssh2_shared` and `libssh2_libssh2_static` targets.
- allow using `find_package(libssh2)` in dependents as an alternative
to `find_package(Libssh2)`.
Co-authored-by: Radek Brich
Suggested-by: Haowei Hsu
Fixes#1103Fixes#731Closes#1104