CPS installation issues

[seisman]

As reported in seismo-learn/seismology101#81.

At least following libraries are needed:

• X11
• ncurses
• termcap and/or terminfo

[core-man]

I don't know if we need ncurses, termcap and/or terminfo.

[seisman]

These libraries may be needed by gsac only. So not a big issue.