An initial attempt to normalize CTRL handling across modes.

This make curses mode try to map ctrl chars, but fall back to the
old behaviour of keeping the ctrl char.

In SDL, this is just a code cleanup.

src/conio/curs_cio.c

@@ -933,6 +933,7 @@ void curs_setcursortype(int type) {
 int curs_getch(void)
 {
 	wint_t ch;
+	wint_t newch;
 #ifdef NCURSES_VERSION_MAJOR
 	MEVENT mevnt;
 #endif
@@ -1160,8 +1161,10 @@ int curs_getch(void)
 
 			default:
 				// Don't translate CTRL-x "keys"...
-				if (ch >= 32)
-					ch = cpchar_from_unicode_cpoint(getcodepage(), ch, 0);
+				newch = cpchar_from_unicode_cpoint(getcodepage(), ch, 0);
+				if (newch == 0 && ch < 32)
+					newch = ch;
+				ch = newch;
 				break;
 		}
 	}

src/conio/sdl_con.c

@@ -992,7 +992,6 @@ void sdl_video_event_thread(void *data)
 					sdl_add_key_uc(sdl_get_char_code(ev.key.keysym.sym, ev.key.keysym.mod), &cvstat);
 				}
 				else if (!isprint(ev.key.keysym.sym)) {
-					if (ev.key.keysym.sym < 128)
 					sdl_add_key_uc(ev.key.keysym.sym, &cvstat);
 				}
 				break;