Wrap WSAPoll in a function

Instead of using a macro, which breaks when the implementation is
compiled separately, add a detail::poll() function, that dispatches to
either ::poll() or WSAPoll().

Author: falbrechtskirchinger

httplib.h

@@ -194,7 +194,6 @@ using ssize_t = long;
 
 using socket_t = SOCKET;
 using socklen_t = int;
-#define poll(fds, nfds, timeout) WSAPoll(fds, nfds, timeout)
 
 #else // not _WIN32
 
@@ -3240,6 +3239,14 @@ inline ssize_t send_socket(socket_t sock, const void *ptr, size_t size,
   });
 }
 
+inline int poll(struct pollfd *fds, nfds_t nfds, int timeout) {
+#ifdef _WIN32
+  return WSAPoll(fds, nfds, timeout);
+#else
+  return ::poll(fds, nfds, timeout);
+#endif
+}
+
 template <bool Read>
 inline ssize_t select_impl(socket_t sock, time_t sec, time_t usec) {
   struct pollfd pfd;
@@ -10377,8 +10384,4 @@ inline SSL_CTX *Client::ssl_context() const {
 
 } // namespace httplib
 
-#ifdef _WIN32
-#undef poll
-#endif
-
 #endif // CPPHTTPLIB_HTTPLIB_H