added simple-flip shader

added simple-flip shader.
options: flip screen horizontally and vertically

data/shaders/simple-flip.glsl

@@ -0,0 +1,41 @@
+/*
+[configuration]
+
+[OptionRangeInteger]
+GUIName = Flip Horizontally
+OptionName = G_FLIP_HORZ
+MinValue = 0
+MaxValue = 1
+StepAmount = 1
+DefaultValue = 1
+
+[OptionRangeInteger]
+GUIName = Flip Vertically
+OptionName = G_FLIP_VERT
+MinValue = 0
+MaxValue = 1
+StepAmount = 1
+DefaultValue = 0
+
+[/configuration]
+*/
+
+void main()
+{
+  vec2 uv = GetCoordinates();
+  vec2 ts = GetInvResolution();
+
+  vec2 pos = uv;
+
+  if (GetOption(G_FLIP_HORZ) == 1) {
+    pos.x = 1.0 - pos.x;
+  }
+  
+  if (GetOption(G_FLIP_VERT) == 1) {
+    pos.y = 1.0 - pos.y;
+  }
+
+  vec4 sum = SampleLocation(pos);
+
+  SetOutput(saturate(sum));
+}