Made Matrix a typedef to Matrixf, and converted the old Matrix to Matrixf, as

part of prep for supporting both Matrixf (float) and Matrixd (double).

Added osg::Matrixf::glLoadMatrix() and osg::Matrixf::glMultiMatrix() methods
and changed corresponding usage of glLoad/MultMatrixf() calls across to use these
methods. Again prep for support Matrixd.

Fixes for VisualStudio 6.0 compile.

src/osg/TexMat.cpp

@@ -27,6 +27,6 @@ TexMat::~TexMat()
 void TexMat::apply(State&) const
 {
     glMatrixMode( GL_TEXTURE );
-    glLoadMatrixf( _matrix.ptr() );
-    glMatrixMode( GL_MODELVIEW ); // fix! GWM Aug 2001
+    _matrix.glLoadMatrix();
+    glMatrixMode( GL_MODELVIEW );
 }