Improved the handling of matrices in serialization so that it's more reliable,

change was to use doubles for reading and writing matrices regardless of type of Matrix
being serialized.

Change does break backwards compatibility though, so code
path supporting original format has been left in for the
time being.  However, this code is not reliable enough and
is over complicated compared to the simplified handling.   Once
the new code has been bedded down for a while I'll remove this code block.

include/osgDB/DataTypes

@@ -84,8 +84,9 @@ struct ObjectGLenum
 #define GLENUM(value) osgDB::ObjectGLenum(value)
 #define DEF_GLENUM(var) osgDB::ObjectGLenum var;
 
-struct ObjectProperty
+class ObjectProperty
 {
+public:
     ObjectProperty( const char* name, int value=0, bool useMap=false )
     : _name(name), _value(value), _mapProperty(useMap) {}
     
@@ -101,6 +102,9 @@ struct ObjectProperty
     std::string _name;
     int _value;
     bool _mapProperty;
+
+protected:
+    ObjectProperty():_value(0),_mapProperty(false) {}
 };
 static ObjectProperty defaultProp("");
 
@@ -109,8 +113,9 @@ static ObjectProperty defaultProp("");
 #define DEF_PROPERTY(name, var) osgDB::ObjectProperty var(name);
 #define DEF_MAPPEE(pairName, var) osgDB::ObjectProperty var(#pairName, 0, true);
 
-struct ObjectMark
+class ObjectMark
 {
+public:
     ObjectMark( const char* name, int delta=0 )
     : _name(name), _indentDelta(delta) {}
     
@@ -119,6 +124,9 @@ struct ObjectMark
     
     std::string _name;
     int _indentDelta;
+
+protected:
+    ObjectMark():_indentDelta(0) {}
 };
 static ObjectMark BEGIN_BRACKET("{", +INDENT_VALUE);
 static ObjectMark END_BRACKET  ("}", -INDENT_VALUE);