video/blit: fix -Wimplicit-fallthrough warnings

src/joystick/linux/SDL_sysjoystick.c

@@ -1449,6 +1449,7 @@ static void HandleInputEvents(SDL_Joystick *joystick)
                         HandleHat(SDL_EVDEV_GetEventTimestamp(event), joystick, hat_index, code % 2, event->value);
                         break;
                     }
+                    SDL_FALLTHROUGH;
                 default:
                     event->value = AxisCorrect(joystick, code, event->value);
                     SDL_SendJoystickAxis(SDL_EVDEV_GetEventTimestamp(event), joystick,
@@ -1521,6 +1522,7 @@ static void HandleClassicEvents(SDL_Joystick *joystick)
                         HandleHat(timestamp, joystick, hat_index, code % 2, events[i].value);
                         break;
                     }
+                    SDL_FALLTHROUGH;
                 default:
                     SDL_SendJoystickAxis(timestamp, joystick,
                                             joystick->hwdata->abs_map[code],

src/video/SDL_blit_1.c

@@ -138,6 +138,7 @@ static void Blit1to2(SDL_BlitInfo *info)
             case 3:
                 *(Uint16 *)dst = map[*src++];
                 dst += 2;
+                SDL_FALLTHROUGH;
             case 2:
                 *(Uint32 *)dst = (map[src[HI]] << 16) | (map[src[LO]]);
                 src += 2;
@@ -167,6 +168,7 @@ static void Blit1to2(SDL_BlitInfo *info)
             case 3:
                 *(Uint16 *)dst = map[*src++];
                 dst += 2;
+                SDL_FALLTHROUGH;
             case 2:
                 *(Uint32 *)dst = (map[src[HI]] << 16) | (map[src[LO]]);
                 src += 2;
@@ -268,8 +270,10 @@ static void Blit1to4(SDL_BlitInfo *info)
         switch (width & 3) {
         case 3:
             *dst++ = map[*src++];
+            SDL_FALLTHROUGH;
         case 2:
             *dst++ = map[*src++];
+            SDL_FALLTHROUGH;
         case 1:
             *dst++ = map[*src++];
         }

src/video/SDL_blit_N.c

@@ -993,9 +993,11 @@ static void Blit_RGB888_index8(SDL_BlitInfo *info)
             case 3:
                 RGB888_RGB332(*dst++, *src);
                 ++src;
+                SDL_FALLTHROUGH;
             case 2:
                 RGB888_RGB332(*dst++, *src);
                 ++src;
+                SDL_FALLTHROUGH;
             case 1:
                 RGB888_RGB332(*dst++, *src);
                 ++src;
@@ -1037,10 +1039,12 @@ static void Blit_RGB888_index8(SDL_BlitInfo *info)
                 RGB888_RGB332(Pixel, *src);
                 *dst++ = map[Pixel];
                 ++src;
+                SDL_FALLTHROUGH;
             case 2:
                 RGB888_RGB332(Pixel, *src);
                 *dst++ = map[Pixel];
                 ++src;
+                SDL_FALLTHROUGH;
             case 1:
                 RGB888_RGB332(Pixel, *src);
                 *dst++ = map[Pixel];
@@ -1103,9 +1107,11 @@ static void Blit_RGB101010_index8(SDL_BlitInfo *info)
             case 3:
                 RGB101010_RGB332(*dst++, *src);
                 ++src;
+                SDL_FALLTHROUGH;
             case 2:
                 RGB101010_RGB332(*dst++, *src);
                 ++src;
+                SDL_FALLTHROUGH;
             case 1:
                 RGB101010_RGB332(*dst++, *src);
                 ++src;
@@ -1147,10 +1153,12 @@ static void Blit_RGB101010_index8(SDL_BlitInfo *info)
                 RGB101010_RGB332(Pixel, *src);
                 *dst++ = map[Pixel];
                 ++src;
+                SDL_FALLTHROUGH;
             case 2:
                 RGB101010_RGB332(Pixel, *src);
                 *dst++ = map[Pixel];
                 ++src;
+                SDL_FALLTHROUGH;
             case 1:
                 RGB101010_RGB332(Pixel, *src);
                 *dst++ = map[Pixel];
@@ -1242,6 +1250,7 @@ static void Blit_RGB888_RGB555(SDL_BlitInfo *info)
                 RGB888_RGB555(dst, src);
                 ++src;
                 ++dst;
+                SDL_FALLTHROUGH;
             case 2:
                 RGB888_RGB555_TWO(dst, src);
                 src += 2;
@@ -1273,6 +1282,7 @@ static void Blit_RGB888_RGB555(SDL_BlitInfo *info)
                 RGB888_RGB555(dst, src);
                 ++src;
                 ++dst;
+                SDL_FALLTHROUGH;
             case 2:
                 RGB888_RGB555_TWO(dst, src);
                 src += 2;
@@ -1370,6 +1380,7 @@ static void Blit_RGB888_RGB565(SDL_BlitInfo *info)
                 RGB888_RGB565(dst, src);
                 ++src;
                 ++dst;
+                SDL_FALLTHROUGH;
             case 2:
                 RGB888_RGB565_TWO(dst, src);
                 src += 2;
@@ -1401,6 +1412,7 @@ static void Blit_RGB888_RGB565(SDL_BlitInfo *info)
                 RGB888_RGB565(dst, src);
                 ++src;
                 ++dst;
+                SDL_FALLTHROUGH;
             case 2:
                 RGB888_RGB565_TWO(dst, src);
                 src += 2;
@@ -1472,9 +1484,11 @@ static void Blit_RGB565_32(SDL_BlitInfo *info, const Uint32 *map)
         case 3:
             *dst++ = RGB565_32(dst, src, map);
             src += 2;
+            SDL_FALLTHROUGH;
         case 2:
             *dst++ = RGB565_32(dst, src, map);
             src += 2;
+            SDL_FALLTHROUGH;
         case 1:
             *dst++ = RGB565_32(dst, src, map);
             src += 2;