Update libssh2 submodule to track back from https://github.com/libssh…

…2/libssh2 (alexcrichton#205)

* Update libssh2 submodule to track back from https://github.com/libssh2/libssh2

* Update sys crate to track latest change from https://github.com/libssh2/libssh2

Update libssh2 submodule to track back from https://github.com/libssh…

…2/libssh2 (alexcrichton#205)

* Update libssh2 submodule to track back from https://github.com/libssh2/libssh2

* Update sys crate to track latest change from https://github.com/libssh2/libssh2

bump version to prep for a release

libssh2-sys: Add support for zlib-ng (alexcrichton#197)

Update to libz-sys 1.1.0, which supports zlib-ng. Provide a feature
zlib-ng-compat to allow building with zlib-ng. Since doing so statically
links zlib-ng, ensure that this feature prevents using a system libssh2.

gersion bump to reflect bundled libssh2 change

refs: alexcrichton#187
refs: alexcrichton#191

gersion bump to reflect bundled libssh2 change

refs: alexcrichton#187
refs: alexcrichton#191

tag it!

tagging 0.8.0