Fixes Debian sid schroot build. Also add build deps required for full testing: tmux, less (for window-resize.test)
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
None of the previous tests even ran the mosh script unless tmux ≥ 1.8 is installed. Thus ‘make check’ was “passing” on, e.g., RHEL 6 even though its Perl is too old (5.10.1). Signed-off-by: Anders Kaseorg <andersk@mit.edu>