notcurses-info: show whether we're using gpm

src/info/main.c

@@ -399,6 +399,7 @@ tinfo_debug_styles(const notcurses* nc, struct ncplane* n, const char* indent){
   tinfo_debug_cap(n, "u7", get_escape(ti, ESCAPE_U7));
   tinfo_debug_cap(n, "ccc", ti->caps.can_change_colors);
   tinfo_debug_cap(n, "rgb", ti->caps.rgb);
+  tinfo_debug_cap(n, "gpm", ti->gpmfd >= 0);
   finish_line(n);
   ncplane_putstr(n, indent);
   tinfo_debug_cap(n, "utf8", ti->caps.utf8);
@@ -438,6 +439,8 @@ int main(int argc, const char** argv){
   if(nc == NULL){
     return EXIT_FAILURE;
   }
+  // so that we know whether we're talking to gpm
+  notcurses_mouse_enable(nc);
   const char indent[] = "";
   int dimx;
   struct ncplane* stdn = notcurses_stddim_yx(nc, NULL, &dimx);