Changed enums to use XXX_COUNT for the count or number of values

Fixes https://github.com/libsdl-org/SDL/issues/10763

test/testpen.c

@@ -19,7 +19,7 @@ typedef struct Pen
 {
     SDL_PenID pen;
     Uint8 r, g, b;
-    float axes[SDL_PEN_NUM_AXES];
+    float axes[SDL_PEN_AXIS_COUNT];
     float x;
     float y;
     Uint32 buttons;