Use FindCurses to find curses libraries

- Some systems have the FindCurses.cmake module to find
  the curses/ncurses libraries using find_package(). And
  in some CheckLibraries is not very reliable, so as
  fallback FindCurses is now used if no other option
  works.
Merge pull request #184 from equalsraf/tb-curses

Use FindCurses.cmake as fallback to find curses libraries