Shaders: work on fullscreen, cleanup creation

shader/texture2D/alphaDivide.vert

@@ -1,8 +1,7 @@
 #version 450 core
-layout(location = 0) in vec2 position;
-layout(location = 1) in vec2 texpos;
+layout (std140, binding = 2) uniform PosTex { vec4 posTex[6]; };
 out vec2 vTexPos;
 void main() {
-  gl_Position = vec4(position, 0, 1);
-  vTexPos = texpos;
+  gl_Position = vec4(posTex[gl_VertexID].xy,0,1);
+  vTexPos = posTex[gl_VertexID].zw;
 }