script_drawing.cpp fallthrough warnings to fix

    ^~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp: In function ‘void do_drawbitmapexr(BITMAP*, int*, int, int)’:
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:2401:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
      pivot_sprite_v_flip(bmp, subBmp, dx, dy, cx, cy, degrees_to_fixed(rot));
      ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:2403:6: note: here
      case 8:
      ^~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:2676:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
      pivot_sprite_v_flip(bmp, subBmp, dx, dy, cx, cy, degrees_to_fixed(rot));
      ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:2678:6: note: here
      case 8:
      ^~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:2952:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
      pivot_sprite_v_flip(bmp, subBmp, dx, dy,  cx,  cy, degrees_to_fixed(rot));
      ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:2954:6: note: here
      case 8:
      ^~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:3224:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
      pivot_sprite_v_flip(bmp, subBmp, dx, dy, cx, cy, degrees_to_fixed(rot));
      ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:3226:6: note: here
      case 8:
      ^~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp: In function ‘void bmp_do_drawbitmapexr(BITMAP*, int*, int, int)’:
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:5316:57: warning: this statement may fall through [-Wimplicit-fallthrough=]
       destBMP = zscriptDrawingRenderTarget->GetBitmapPtr(bitmapIndex);
                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:5318:3: note: here
   default: destBMP = FFCore.get_user_bitmap(bitmapIndex);
   ^~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:5419:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
      pivot_sprite_v_flip(destBMP, subBmp, dx, dy, cx, cy, degrees_to_fixed(rot));
      ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:5421:6: note: here
      case 8:
      ^~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:5694:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
      pivot_sprite_v_flip(destBMP, subBmp, dx, dy, cx, cy, degrees_to_fixed(rot));
      ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:5696:6: note: here
      case 8:
      ^~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:5970:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
      pivot_sprite_v_flip(destBMP, subBmp, dx, dy,  cx,  cy, degrees_to_fixed(rot));
      ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:5972:6: note: here
      case 8:
      ^~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:6242:25: warning: this statement may fall through [-Wimplicit-fallthrough=]
      pivot_sprite_v_flip(destBMP, subBmp, dx, dy, cx, cy, degrees_to_fixed(rot));
      ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/peter/Projects/ZeldaClassic/src/script_drawing.cpp:6244:6: note: here
      case 8:
      ^~~~