Implemented lighten, darken, saturate, and desaturate built-ins.

context.cpp

@@ -109,12 +109,16 @@ namespace Sass {
     register_function(blue_sig, blue);
     register_function(mix_sig, mix);
     // HSL Functions
-    register_function(hsla_sig, hsla);
     register_function(hsl_sig, hsl);
+    register_function(hsla_sig, hsla);
     register_function(hue_sig, hue);
     register_function(saturation_sig, saturation);
     register_function(lightness_sig, lightness);
     register_function(adjust_hue_sig, adjust_hue);
+    register_function(lighten_sig, lighten);
+    register_function(darken_sig, darken);
+    register_function(saturate_sig, saturate);
+    register_function(desaturate_sig, desaturate);
     register_function(adjust_color_sig, adjust_color);
     register_function(change_color_sig, change_color);
     register_function(invert_sig, invert);

functions.hpp

@@ -86,12 +86,12 @@ namespace Sass {
     
     // HSL Functions ///////////////////////////////////////////////////////
     
-    extern Signature hsla_sig;
-    Node hsla(const Node, Environment&, Node_Factory&);
-    
     extern Signature hsl_sig;
     Node hsl(const Node, Environment&, Node_Factory&);
 
+    extern Signature hsla_sig;
+    Node hsla(const Node, Environment&, Node_Factory&);
+    
     extern Signature hue_sig;
     Node hue(const Node, Environment&, Node_Factory&);
 
@@ -104,11 +104,17 @@ namespace Sass {
     extern Signature adjust_hue_sig;
     Node adjust_hue(const Node, Environment&, Node_Factory&);
 
-    extern Signature adjust_color_sig;
-    Node adjust_color(const Node, Environment&, Node_Factory&);
+    extern Signature lighten_sig;
+    Node lighten(const Node, Environment&, Node_Factory&);
 
-    extern Signature change_color_sig;
-    Node change_color(const Node, Environment&, Node_Factory&);
+    extern Signature darken_sig;
+    Node darken(const Node, Environment&, Node_Factory&);
+
+    extern Signature saturate_sig;
+    Node saturate(const Node, Environment&, Node_Factory&);
+
+    extern Signature desaturate_sig;
+    Node desaturate(const Node, Environment&, Node_Factory&);
 
     extern Signature invert_sig;
     Node invert(const Node, Environment&, Node_Factory&);
@@ -127,6 +133,14 @@ namespace Sass {
     extern Signature fade_out_sig;
     Node transparentize(const Node, Environment&, Node_Factory&);
 
+    // Other Color Functions ///////////////////////////////////////////////
+    
+    extern Signature adjust_color_sig;
+    Node adjust_color(const Node, Environment&, Node_Factory&);
+
+    extern Signature change_color_sig;
+    Node change_color(const Node, Environment&, Node_Factory&);
+
     // String Functions ////////////////////////////////////////////////////
 
     extern Signature unquote_sig;