Core (LV::Palette): Add comparison operators.

Author: kaixiong

libvisual/libvisual/lv_palette.h

@@ -70,6 +70,16 @@ namespace LV {
           return *this;
       }
 
+      constexpr friend bool operator== (Palette const& lhs, Palette const& rhs)
+      {
+          return lhs.colors == rhs.colors;
+      }
+
+      constexpr friend bool operator!= (Palette const& lhs, Palette const& rhs)
+      {
+          return !(lhs == rhs);
+      }
+
       bool empty () const
       {
           return colors.empty ();