There is no MMX code for (add|put|put_signed)_pixels_clamped
since commit bfb28b5ce89f3e950214b67ea95b45e3355c2caf, so use
declare_func instead of declare_func_emms() to also test that
we are not in MMX mode after return.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>