#13 Fix build warning on ncurses-6.3

[Sergei Trofimovich]

ncuses-6.3 added printf-style function attributes and now makes
it easier to catch cases when user input is used in palce of format
string when built with CFLAGS=-Werror=format-security:

aewan.c: In function 'paint_screen':
aewan.c:147:7: error: format not a string literal and no format arguments [-Werror=format-security]
  147 |       printw(msg);
      |       ^~~~~~

Attached patch that fixes build for me.

[Ricardo Mones]

Yes, please apply Sergei's patch, I had to make the same for fixing builds within Debian packaging:
https://salsa.debian.org/debian/aewan/-/blob/master/debian/patches/format-security.patch
But would be nice to have it applied upstream.
Thanks!