router_t methods should not allocate memory for lookup in outpipes

[sigiesec]

E.g. at

libzmq/src/router.cpp

Line 211 in cfef040

blob_t routing_id ((unsigned char*) msg_->data (), msg_->size ());

a blob_t is constructed just to use it as an argument for outpipes.find. Since blob_t is std::basic_string, it will allocate memory. blob_t should be redefined to a type which allows referencing existing memory instead.

Severals similar uses exist in router_t and in some other classes.