OpenGL2: remove lightmap support from generic glsl shader.

This path was barely used and doing this compiles fewer shaders.

code/renderergl2/glsl/generic_vp.glsl

@@ -9,7 +9,7 @@ attribute vec3 attr_Normal2;
 attribute vec4 attr_Color;
 attribute vec4 attr_TexCoord0;
 
-#if defined(USE_LIGHTMAP) || defined(USE_TCGEN)
+#if defined(USE_TCGEN)
 attribute vec4 attr_TexCoord1;
 #endif
 
@@ -57,9 +57,6 @@ uniform float  u_VertexLerp;
 #endif
 
 varying vec2   var_DiffuseTex;
-#if defined(USE_LIGHTMAP)
-varying vec2   var_LightTex;
-#endif
 varying vec4   var_Color;
 
 #if defined(USE_DEFORM_VERTEXES)
@@ -230,10 +227,6 @@ void main()
     var_DiffuseTex = tex;
 #endif
 
-#if defined(USE_LIGHTMAP)
-	var_LightTex = attr_TexCoord1.st;
-#endif
-
 #if defined(USE_RGBAGEN)
 	var_Color = CalcColor(position, normal);
 #else