Fix regression in svg output and simplify viewport handling (bug #44765) * gl2ps-renderer.cc (glps-renderer::draw): remove check for GL2PS_NO_FEEDBACK, it it always true after EndViewport * gl2ps-renderer.h (glps-renderer::draw_axes): call gl2psBegin(End)Viewport for every axes and check for GL2PS_NO_FEEDBACK after each axes. * gl2ps-renderer.h (glps-renderer::draw_axes):remove unnecessary "naxes" attribute

# u_vr.m

## define and exectute "__demo__" once
eval ("function __demo__ ();  df_vr;  v = vr * 2; endfunction");
__demo__;

## clear definition of "__demo__"
clear __demo__

## define and exectute "__demo__" once more
eval ("function __demo__ ();  df_vr;  v = vr * 2; endfunction");
__demo__;