UpnpString_set_String() and UpnpString_set_StringN now return error values. String lenghts are size_t. (cherry picked from commit 81b28fbb9073b8b3ea5724e5b7c11b29c44f9be4)
git-svn-id: https://pupnp.svn.sourceforge.net/svnroot/pupnp/branches/branch-1.6.x@537 119443c7-1b9e-41f8-b6fc-b9c35fce742c