tests: support spaces in paths to SSH, SSHD and SFTP binaries

First patch to enable Windows support using Cygwin-based OpenSSH.
tests: use Cygwin-style paths in SSH, SSHD and SFTP config files

Second patch to enable Windows support using Cygwin-based OpenSSH.

Tested with CopSSH 5.0.0 free edition using an msys shell on Windows 7.