* ldexp.h (node_type): Add etree_provided.
* ldexp.c (exp_fold_tree): Handle etree_provided. Set the node
type to etree_provided if defined by PROVIDE. Allow updating
for etree_provided.
(exp_print_tree): Handle etree_provided.
* mpw-elfmips.c (gldelf32ebmip_find_exp_assignment): Handle
etree_provided.