gl_shader_decompiler: Implement clip distances

src/video_core/engines/shader_bytecode.h

@@ -82,6 +82,8 @@ union Attribute {
         Position = 7,
         Attribute_0 = 8,
         Attribute_31 = 39,
+        ClipDistances0123 = 44,
+        ClipDistances4567 = 45,
         PointCoord = 46,
         // This attribute contains a tuple of (~, ~, InstanceId, VertexId) when inside a vertex
         // shader, and a tuple of (TessCoord.x, TessCoord.y, TessCoord.z, ~) when inside a Tess Eval