[rshapes] Fix incorrect parameter names in DrawRectangleGradientEx

Examining the code shows that the rectangle is drawn winding counterclockwise, starting
with the top left. Therefore the colors used should be in the order: topLeft, bottomLeft,
bottomRight, topRight.

However, the variables actually being used are topLeft, bottomLeft, topRight,
bottomRight. I was confused by this as I was getting striping where I didn't expect any.
Put another way, the last two parameters are misnamed.

This diff swaps the parameter names and their usages. The result is that no runtime
behaviour changes: the same parameter order yields the same visual result both before and
after this change, but the parameter names now correctly reflect what they are actually
used for.

You can actually see this in the implementation of DrawRectangleGradientV, which
(correctly) passes top, bottom, bottom, top to DrawRectangleGradientEx.

src/raylib.h

@@ -1273,7 +1273,7 @@ RLAPI void DrawRectangleRec(Rectangle rec, Color color);
 RLAPI void DrawRectanglePro(Rectangle rec, Vector2 origin, float rotation, Color color);                 // Draw a color-filled rectangle with pro parameters
 RLAPI void DrawRectangleGradientV(int posX, int posY, int width, int height, Color top, Color bottom);   // Draw a vertical-gradient-filled rectangle
 RLAPI void DrawRectangleGradientH(int posX, int posY, int width, int height, Color left, Color right);   // Draw a horizontal-gradient-filled rectangle
-RLAPI void DrawRectangleGradientEx(Rectangle rec, Color topLeft, Color bottomLeft, Color topRight, Color bottomRight); // Draw a gradient-filled rectangle with custom vertex colors
+RLAPI void DrawRectangleGradientEx(Rectangle rec, Color topLeft, Color bottomLeft, Color bottomRight, Color topRight); // Draw a gradient-filled rectangle with custom vertex colors
 RLAPI void DrawRectangleLines(int posX, int posY, int width, int height, Color color);                   // Draw rectangle outline
 RLAPI void DrawRectangleLinesEx(Rectangle rec, float lineThick, Color color);                            // Draw rectangle outline with extended parameters
 RLAPI void DrawRectangleRounded(Rectangle rec, float roundness, int segments, Color color);              // Draw rectangle with rounded edges

src/rshapes.c

@@ -774,7 +774,7 @@ void DrawRectangleGradientH(int posX, int posY, int width, int height, Color lef
 }
 
 // Draw a gradient-filled rectangle
-void DrawRectangleGradientEx(Rectangle rec, Color topLeft, Color bottomLeft, Color topRight, Color bottomRight)
+void DrawRectangleGradientEx(Rectangle rec, Color topLeft, Color bottomLeft, Color bottomRight, Color topRight)
 {
     rlSetTexture(GetShapesTexture().id);
     Rectangle shapeRect = GetShapesTextureRectangle();
@@ -791,11 +791,11 @@ void DrawRectangleGradientEx(Rectangle rec, Color topLeft, Color bottomLeft, Col
         rlTexCoord2f(shapeRect.x/texShapes.width, (shapeRect.y + shapeRect.height)/texShapes.height);
         rlVertex2f(rec.x, rec.y + rec.height);
 
-        rlColor4ub(topRight.r, topRight.g, topRight.b, topRight.a);
+        rlColor4ub(bottomRight.r, bottomRight.g, bottomRight.b, bottomRight.a);
         rlTexCoord2f((shapeRect.x + shapeRect.width)/texShapes.width, (shapeRect.y + shapeRect.height)/texShapes.height);
         rlVertex2f(rec.x + rec.width, rec.y + rec.height);
 
-        rlColor4ub(bottomRight.r, bottomRight.g, bottomRight.b, bottomRight.a);
+        rlColor4ub(topRight.r, topRight.g, topRight.b, topRight.a);
         rlTexCoord2f((shapeRect.x + shapeRect.width)/texShapes.width, shapeRect.y/texShapes.height);
         rlVertex2f(rec.x + rec.width, rec.y);
     rlEnd();