i386: replace g_malloc()+memcpy() with g_memdup()

I found these pattern via grepping the source tree. I don't have a
coccinelle script for it!

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>