Added lighting engine module

- New lighting engine module which contains new data types Light and
Material. These data types and functions facilitates making a basic 3D
iluminated program with a light and a model.

- Added lighting engine module example (currently included in raylib.h;
it might be compiled by separate and include lighting.h in game source C
file).

- Corrected some opengl defines control structures and added some TODO
to fix raylib-opengl 1.1 source build (note: now source can be compiled
without errors, but rlglReadPixels() won't work properly).

Note: most of functions of phong version 330 shader are not in v100
shaders, so I couldn't write a version 100 phong shader. These functions
are included from version 150.

examples/resources/shaders/phong.vs

@@ -0,0 +1,28 @@
+#version 330
+
+// Vertex input data
+in vec3 vertexPosition;
+in vec2 vertexTexCoord;
+in vec3 vertexNormal;
+
+// Projection and model data
+uniform mat4 projectionMatrix;
+uniform mat4 modelviewMatrix;
+uniform mat4 modelMatrix;
+
+// Attributes to fragment shader
+out vec2 fragTexCoord;
+out vec3 fragNormal;
+
+void main()
+{
+    // Send texture coord to fragment shader
+    fragTexCoord = vertexTexCoord;
+    
+    // Calculate view vector normal from model
+    mat3 normalMatrix = transpose(inverse(mat3(modelMatrix)));
+    fragNormal = normalize(normalMatrix * vertexNormal);
+    
+    // Calculate final vertex position
+    gl_Position = projectionMatrix * modelviewMatrix * vec4(vertexPosition, 1.0);
+}