Fix dom element attribute setting to return the old element as per the API
Fix dom element attribute setting to return the old element as per the API

svn path=/trunk/libdom/; revision=13561

prepare/netsurf_libdom,prepare/netsurf_libdom,Achal-Aggarwal/libdom,prepare/netsurf_libdom,prepare/netsurf_libdom,Achal-Aggarwal/libdom,dunkelstern/libdom,dunkelstern/libdom,Achal-Aggarwal/libdom,Achal-Aggarwal/libdom,prepare/netsurf_libdom,dunkelstern/libdom,Achal-Aggarwal/libdom,prepare/netsurf_libdom,dunkelstern/libdom,dunkelstern/libdom,Achal-Aggarwal/libdom,dunkelstern/libdom