Update libssh2 to use the newest version from git. This caused a
transition from released version number to hash as it has not been
version rev'd in over a year (see issue
https://github.com/libssh2/libssh2/issues/220 for bump request).
This brings in changes to the autoconf to correctly pick the crypto
library.
Signed-off-by: Sam Voss <sam.voss@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
