Snd 21.7

s7: added (*s7* 'muffle-warnings?) and s7_output_string
    bool s7_flush_output_port (was void)

checked: notcurses 2.3.13, sbcl 2.1.8
  notcurses 2.3.17 behaves very strangely in row 0, so I've covered row 0
  with a header box.  It's probably some new notcurses configuration option.

Thanks!:  Brad Christensen, Woody Douglass, JGM, Anders Vinjar
