Added scissor test and mouse painting examples proposed in #890 (#919)

- Updated Makefile with new examples

examples/core/core_scissor_test.c

@@ -0,0 +1,77 @@
+/*******************************************************************************************
+*
+*   raylib [core] example - Scissor test
+*
+*   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) 2019 Chris Dill (@MysteriousSpace)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    InitWindow(screenWidth, screenHeight, "raylib [core] example - scissor test");
+
+    Rectangle scissorArea = { 0, 0, 300, 300};
+    bool scissorMode = true;
+
+    SetTargetFPS(60);
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        if (IsKeyPressed(KEY_S))
+        {
+            scissorMode = !scissorMode;
+        }
+
+        // Centre the scissor area around the mouse position
+        scissorArea.x = GetMouseX() - scissorArea.width / 2;
+        scissorArea.y = GetMouseY() - scissorArea.height / 2;
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+            ClearBackground(RAYWHITE);
+
+            if (scissorMode)
+            {
+                BeginScissorMode(scissorArea.x, scissorArea.y, scissorArea.width, scissorArea.height);
+            }
+
+            DrawRectangle(80, 45, 640, 360, RED);
+            DrawRectangleLines(80, 45, 640, 360, BLACK);
+            DrawText("Move the mouse around to reveal this text!", 190, 200, 20, LIGHTGRAY);
+
+            if (scissorMode)
+            {
+                EndScissorMode();
+            }
+
+            DrawRectangleLinesEx(scissorArea, 2, BLACK);
+            DrawText("Press s to toggle scissor test", 10, 10, 20, DARKGRAY);
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}