char/chan: clean up MovingPartScalar/CharacterSlider constructors

These changes are a follow-up to 8b6f82256e31e7840c60775c8f2f9e1084aae972 but could not be made on that branch due to ABI compatibility reasons.

panda/src/chan/movingPartScalar.I

@@ -25,7 +25,7 @@ MovingPartScalar(const MovingPartScalar &copy) :
  */
 INLINE MovingPartScalar::
 MovingPartScalar(PartGroup *parent, const std::string &name,
-                 const PN_stdfloat &default_value)
+                 PN_stdfloat default_value)
   : MovingPart<ACScalarSwitchType>(parent, name, default_value) {
 }
 

panda/src/chan/movingPartScalar.h

@@ -31,7 +31,7 @@ protected:
 
 public:
   INLINE MovingPartScalar(PartGroup *parent, const std::string &name,
-                          const PN_stdfloat &default_value = 0);
+                          PN_stdfloat default_value = 0);
   virtual ~MovingPartScalar();
 
   virtual void get_blend_value(const PartBundle *root);

panda/src/char/characterSlider.cxx

@@ -40,15 +40,8 @@ CharacterSlider(const CharacterSlider &copy) :
  *
  */
 CharacterSlider::
-CharacterSlider(PartGroup *parent, const std::string &name)
-  : MovingPartScalar(parent, name) {
-}
-
-/**
- *
- */
-CharacterSlider::
-CharacterSlider(PartGroup *parent, const std::string &name, const PN_stdfloat &default_value)
+CharacterSlider(PartGroup *parent, const std::string &name,
+                PN_stdfloat default_value)
   : MovingPartScalar(parent, name, default_value) {
 }
 

panda/src/char/characterSlider.h

@@ -31,8 +31,8 @@ protected:
   CharacterSlider(const CharacterSlider &copy);
 
 PUBLISHED:
-  explicit CharacterSlider(PartGroup *parent, const std::string &name);
-  explicit CharacterSlider(PartGroup *parent, const std::string &name, const PN_stdfloat &default_value);
+  explicit CharacterSlider(PartGroup *parent, const std::string &name,
+                           PN_stdfloat default_value = 0);
   virtual ~CharacterSlider();
 
 public: