Suppress sigpipe in sender thread.

src/net/linux/socket_startup.cpp

@@ -26,14 +26,12 @@
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <unistd.h>
-#include <csignal>
 
 using namespace std;
 
 bool
 socket_startup()
 {
-	signal(SIGPIPE, SIG_IGN);
 	return true;
 }