Fix D3D z-buffer problem by having separate GetOrthoMatrix functions for OGL and D3D.

I don't understand why the two APIs create an ortho matrix so differently, but I'm tried of messing with it for now.

stepmania/src/RageMath.cpp

@@ -440,23 +440,6 @@ RageMatrix RageLookAt(
 	return ret;
 }
 
-RageMatrix RageOrtho( float l, float r, float b, float t, float zn, float zf )
-{
-	RageMatrix m(
-		2/(r-l),      0,            0,           0,
-		0,            2/(t-b),      0,           0,
-		0,            0,            -2/(zf-zn),   0,
-		-(r+l)/(r-l), -(t+b)/(t-b), -(zf+zn)/(zf-zn),  1 );
-/*
-	RageMatrix m(
-		2/(r-l),      0,            0,           0,
-		0,            2/(t-b),      0,           0,
-		0,            0,            1/(zf-zn),   0,
-		(l+r)/(l-r),  (t+b)/(b-t),  zn/(zn-zf),  1 );
-*/
-	return m;
-}
-
 RageMatrix RageMatrixIdentity()
 {
 	RageMatrix m;
@@ -464,32 +447,3 @@ RageMatrix RageMatrixIdentity()
 	return m;
 }
 
-RageMatrix RageMatrixFrustrum( 
-	float left,    
-	float right,   
-	float bottom,  
-	float top,     
-	float znear,   
-	float zfar )	// see glFrustrum docs
-{
-	float A = (right+left) / (right-left);
-	float B = (top+bottom) / (top-bottom);
-	float C = -1 * (zfar+znear) / (zfar-znear);
-	float D = -1 * (2*zfar*znear) / (zfar-znear);
-	RageMatrix m(
-		2*znear/(right-left), 0,                   0,  0,
-		0,                   2*znear/(top-bottom), 0,  0,
-		A,                   B,                    C,  -1,
-		0,                   0,                    D,  0 );
-	return m;
-}
-
-RageMatrix RageMatrixPerspective(float fovy, float aspect, float zNear, float zFar)
-{
-   float ymax = zNear * tanf(fovy * PI / 360.0f);
-   float ymin = -ymax;
-   float xmin = ymin * aspect;
-   float xmax = ymax * aspect;
-
-   return RageMatrixFrustrum(xmin, xmax, ymin, ymax, zNear, zFar);
-}