Problem: tcp_address.cpp allowed [ and ] around address

This syntax is undocumented and has no known meaning. It was in libzmq
since 3.x.

Solution: remove this code.

src/tcp_address.cpp

@@ -413,11 +413,6 @@ int zmq::tcp_address_t::resolve (const char *name_, bool local_, bool ipv6_, boo
     std::string addr_str (name_, delimiter - name_);
     std::string port_str (delimiter + 1);
 
-    //  Remove square brackets around the address, if any.
-    if (addr_str.size () >= 2 && addr_str [0] == '[' &&
-          addr_str [addr_str.size () - 1] == ']')
-        addr_str = addr_str.substr (1, addr_str.size () - 2);
-
     //  Allow 0 specifically, to detect invalid port error in atoi if not
     uint16_t port;
     if (port_str == "*" || port_str == "0")