Assume getaddrinfo in C code

Assume getaddrinfo in C code

* admin/CPP-DEFINES, configure.ac: Remove HAVE_GETADDRINFO, HAVE_H_ERRNO.
All uses removed.
* doc/lispref/processes.texi (Network, Network Processes), etc/NEWS:
Say that port numbers can be integer strings.
* lib-src/pop.c (h_errno) [!WINDOWSNT && !HAVE_H_ERRNO]: Remove decl.
(socket_connection): Assume HAVE_GETADDRINFO.
* lisp/mpc.el (mpc--proc-connect):
* lisp/net/network-stream.el (open-network-stream):
It’s now OK to use integer strings as port numbers.
* src/process.c (conv_numerical_to_lisp) [!HAVE_GETADDRINFO]: Remove.
(Fmake_network_process): Assume HAVE_GETADDRINFO.