Batch of 9 new shapes examples!

Some examples included in this batch require the included libraries: `easings.h` and `raygui.h`. Examples included:

 - shapes_bouncing_ball
 - shapes_collision_area
 - shapes_following_eyes
 - shapes_draw_circle_sector (requires raygui.h)
 - shapes_draw_rectangle_rounded (requires raygui.h)
 - shapes_draw_ring (requires raygui.h)
 - shapes_easings_ball_anim (requires easings.h)
 - shapes_easings_box_anim (requires easings.h)
 - shapes_easings_rectangle_array (requires easings.h)

examples/shapes/shapes_following_eyes.c

@@ -0,0 +1,104 @@
+/*******************************************************************************************
+*
+*   raylib [shapes] example - following eyes
+*
+*   This example has been created using raylib 2.5 (www.raylib.com)
+*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
+*
+*   Copyright (c) 2013-2019 Ramon Santamaria (@raysan5)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+
+#include <math.h>       // Required for: atan2f()
+
+int main()
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    InitWindow(screenWidth, screenHeight, "raylib [shapes] example - following eyes");
+    
+    Vector2 scleraLeftPosition = { GetScreenWidth()/2 - 100, GetScreenHeight()/2 };
+    Vector2 scleraRightPosition = { GetScreenWidth()/2 + 100, GetScreenHeight()/2 };
+    float scleraRadius = 80;
+    
+    Vector2 irisLeftPosition = { GetScreenWidth()/2 - 100, GetScreenHeight()/2 };
+    Vector2 irisRightPosition = { GetScreenWidth()/2 + 100, GetScreenHeight()/2};
+    float irisRadius = 24;
+   
+    float angle;  
+    float dx, dy, dxx, dyy; 
+    
+    SetTargetFPS(60);
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        irisLeftPosition = GetMousePosition();
+        irisRightPosition = GetMousePosition();
+        
+        // Check not inside the left eye sclera
+        if (!CheckCollisionPointCircle(irisLeftPosition, scleraLeftPosition, scleraRadius - 20))
+        {
+            dx = irisLeftPosition.x - scleraLeftPosition.x;
+            dy = irisLeftPosition.y - scleraLeftPosition.y;
+        
+            angle = atan2f(dy, dx);
+
+            dxx = (scleraRadius - irisRadius)*cosf(angle);
+            dyy = (scleraRadius - irisRadius)*sinf(angle);
+
+            irisLeftPosition.x = scleraLeftPosition.x + dxx;
+            irisLeftPosition.y = scleraLeftPosition.y + dyy;
+        }
+
+        // Check not inside the right eye sclera
+        if (!CheckCollisionPointCircle(irisRightPosition, scleraRightPosition, scleraRadius - 20))
+        {
+            dx = irisRightPosition.x - scleraRightPosition.x;
+            dy = irisRightPosition.y - scleraRightPosition.y;
+        
+            angle = atan2f(dy, dx);
+
+            dxx = (scleraRadius - irisRadius)*cosf(angle);
+            dyy = (scleraRadius - irisRadius)*sinf(angle);
+
+            irisRightPosition.x = scleraRightPosition.x + dxx;
+            irisRightPosition.y = scleraRightPosition.y + dyy;
+        }
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+            ClearBackground(RAYWHITE);
+
+            DrawCircleV(scleraLeftPosition, scleraRadius, LIGHTGRAY);
+            DrawCircleV(irisLeftPosition, irisRadius, BROWN);
+            DrawCircleV(irisLeftPosition, 10, BLACK);
+            
+            DrawCircleV(scleraRightPosition, scleraRadius, LIGHTGRAY);
+            DrawCircleV(irisRightPosition, irisRadius, DARKGREEN);
+            DrawCircleV(irisRightPosition, 10, BLACK);
+            
+            DrawFPS(10, 10);
+            
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------   
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}