Added a Matrix::value_type typedef'd trait into osg::Matrix, defaulting its

value to float, and converted the internal code across to use value_type.  This
allows Matrix to be converted to use double's simply by change the definition
of value_type.  Added Matrix::glLoadlMatrix and Matrix::glMultMatrix() to
help encapsulate the changes between float and double matrix usage.

Updated code that uses Matrix so it doesn't assume float or double matrices.

src/osgPlugins/osg/TexMat.cpp

@@ -39,11 +39,13 @@ bool TexMat_readLocalData(Object& obj, Input& fr)
         Matrix& matrix = texmat.getMatrix();
     
         int k=0;
+        double v;
         for(int i=0;i<4;++i)
         {
             for(int j=0;j<4;++j)
             {
-                fr[k].getFloat(matrix(i,j));
+                fr[k].getDouble(v);
+                matrix(i,j)=v;
                 k++;
             }
         }