A few changes to startup details

* Even when emitting smcup, emit an explicit screen clear, to handle
  smcup that fills the screen with old background color #1045
* Rather than emitting notcurses_mouse_disable(), emit the more
  powerful (proper superset) reset_term_attributes)
* Emit a diagnostic when we're not connected to a terminal

src/lib/internal.h

@@ -252,6 +252,7 @@ typedef struct tinfo {
   char* getm;     // get mouse events
   bool RGBflag;   // ti-reported "RGB" flag for 24bpc truecolor
   bool CCCflag;   // ti-reported "CCC" flag for palette set capability
+  bool BCEflag;   // ti-reported "BCE" flag for erases with background color
   bool AMflag;    // ti-reported "AM" flag for automatic movement to next line
   char* smcup;    // enter alternate mode
   char* rmcup;    // restore primary mode

src/lib/notcurses.c

@@ -945,7 +945,6 @@ notcurses* notcurses_init(const notcurses_options* opts, FILE* outfp){
   }
   ret->ttyfd = get_tty_fd(ret, ret->ttyfp);
   is_linux_console(ret, !!(opts->flags & NCOPTION_NO_FONT_CHANGES));
-  notcurses_mouse_disable(ret);
   if(ret->ttyfd >= 0){
     if(tcgetattr(ret->ttyfd, &ret->tpreserved)){
       fprintf(stderr, "Couldn't preserve terminal state for %d (%s)\n", ret->ttyfd, strerror(errno));
@@ -975,6 +974,7 @@ notcurses* notcurses_init(const notcurses_options* opts, FILE* outfp){
   }else{
     dimy = 24; // fuck it, lol
     dimx = 80;
+    fprintf(stderr, "Defaulting to %dx%d (output is not to a terminal)\n", dimy, dimx);
   }
   ret->suppress_banner = opts->flags & NCOPTION_SUPPRESS_BANNERS;
   char* shortname_term = termname();
@@ -988,6 +988,7 @@ notcurses* notcurses_init(const notcurses_options* opts, FILE* outfp){
   if(interrogate_terminfo(&ret->tcache)){
     goto err;
   }
+  reset_term_attributes(ret);
   if(ncinputlayer_init(&ret->input, stdin)){
     goto err;
   }
@@ -1029,6 +1030,10 @@ notcurses* notcurses_init(const notcurses_options* opts, FILE* outfp){
         free_plane(ret->top);
         goto err;
       }
+      // explicit clear even though smcup *might* clear
+      if(tty_emit("clear", ret->tcache.clearscr, ret->ttyfd)){
+        notcurses_refresh(ret, NULL, NULL);
+      }
     }else if(!(opts->flags & NCOPTION_NO_ALTERNATE_SCREEN)){
       // if they expected the alternate screen, but we didn't have one to
       // offer, at least clear the screen. try using "clear"; if that doesn't