GCC-6.4 sys/select.h build failures with std=c++14

[Ian Fette <ifette@gmail.com>]

I tried compiling a very simple program with curl using -std=c++14 under
64-bit cygwin with gcc 6.4.0. When compiling with just g++ main.cpp -lcurl
everything is fine, however if I try to use c++14 as the dialect (g++
main.cpp -lcurl -std=c++14) familiar problems creep up

In file included from /usr/include/curl/curl.h:2547:0,
                 from main.cpp:10:
/usr/include/curl/multi.h:155:40: error: ‘fd_set’ has not been declared
                                        fd_set *read_fd_set,
                                        ^~~~~~
/usr/include/curl/multi.h:156:40: error: ‘fd_set’ has not been declared
                                        fd_set *write_fd_set,
                                        ^~~~~~
/usr/include/curl/multi.h:157:40: error: ‘fd_set’ has not been declared
                                        fd_set *exc_fd_set,
                                        ^~~~~~


This is resolved by manually including <sys/select.h> before including
<curl/curl.h>

This was discussed in the curl project in the past (
https://github.com/curl/curl/issues/749) where it was determined that it
was caused by a cygwin bug which was addressed in
https://cygwin.com/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=newlib/libc/include/sys/types.h;h=c9f0fc7f3a9ca420c2372c9af42ce2a0e63e3b1c;hb=ee97c4b22491b205fd3b7697e03c909e02b652d3

If anyone has thoughts, I'd greatly appreciate it. Compiling the following
is sufficient to reproduce.

#include <iostream>
#include <curl/curl.h>

using namespace std;

int main() {

CURL *curl = curl_easy_init();
if(curl) {
  CURLcode res;
  curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
  res = curl_easy_perform(curl);
  curl_easy_cleanup(curl);
}

}

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