OpenGL: fix GPU_SHADER_SIMPLE_LIGHTING_SMOOTH_COLOR

The fragment shader expects a normal, but the vertex shader was not providing one.

Fix: added a new vertex shader that has normals + smooth color interpolation.

I also split gpu_shader_3D_vert in two:
- one with just position
- one with position + normal

For each of the builtin shaders, we should be able to look at the GLSL and tell exactly what it's doing. Using #defines and #ifdefs for rendering options makes the shaders hard to read and easy to break.

source/blender/gpu/shaders/gpu_shader_3D_normal_smooth_color_vert.glsl

@@ -0,0 +1,26 @@
+
+uniform mat4 ModelViewProjectionMatrix;
+uniform mat3 NormalMatrix;
+
+#if __VERSION__ == 120
+  attribute vec3 pos;
+  attribute vec3 nor;
+  attribute vec4 color;
+
+  varying vec4 finalColor;
+  varying vec3 normal;
+#else
+  in vec3 pos;
+  in vec3 nor;
+  in vec4 color;
+
+  out vec3 normal;
+  out vec4 finalColor;
+#endif
+
+void main()
+{
+	normal = normalize(NormalMatrix * nor);
+	gl_Position = ModelViewProjectionMatrix * vec4(pos, 1.0);
+	finalColor = color;
+}

source/blender/gpu/shaders/gpu_shader_3D_normal_vert.glsl

@@ -0,0 +1,19 @@
+
+uniform mat4 ModelViewProjectionMatrix;
+uniform mat3 NormalMatrix;
+
+#if __VERSION__ == 120
+  attribute vec3 pos;
+  attribute vec3 nor;
+  varying vec3 normal;
+#else
+  in vec3 pos;
+  in vec3 nor;
+  out vec3 normal;
+#endif
+
+void main()
+{
+	normal = normalize(NormalMatrix * nor);
+	gl_Position = ModelViewProjectionMatrix * vec4(pos, 1.0);
+}

source/blender/gpu/shaders/gpu_shader_3D_vert.glsl

@@ -1,27 +1,13 @@
 
 uniform mat4 ModelViewProjectionMatrix;
-#ifdef USE_NORMALS
-uniform mat3 NormalMatrix;
-#endif
 
 #if __VERSION__ == 120
   attribute vec3 pos;
-#ifdef USE_NORMALS
-  attribute vec3 nor;
-  varying vec3 normal;
-#endif
 #else
   in vec3 pos;
-#ifdef USE_NORMALS
-  in vec3 nor;
-  out vec3 normal;
-#endif
 #endif
 
 void main()
 {
-#ifdef USE_NORMALS
-	normal = normalize(NormalMatrix * nor);
-#endif
 	gl_Position = ModelViewProjectionMatrix * vec4(pos, 1.0);
 }