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