[cc2-qbe] Add support for NULL parameter in tmpnode()
[cc2-qbe] Add support for NULL parameter in tmpnode()

It is a very common case to call 'newnode(tmpnode(OTMP))'
so it is a good idea to pack it into newnode().

k0gaMSX/scc,k0gaMSX/scc,k0gaMSX/scc