unlinkfile
error = unlinkfile(xc, fileid_src_dir, pcn_src->pcn_name, fileid_src);
error = unlinkfile(xc, fileid, pcn->pcn_name, targ_fileid);
error = unlinkfile(xc, parent_fileid, pcn->pcn_name, targ_fileid);
error = unlinkfile(xc, fileid_targ_dir, pcn_targ->pcn_name,
int unlinkfile(struct Xconn *, fileid_t, const char *, fileid_t);