Add support for setting the SO_REUSEADDR option for sockets

src/platform-macos.cc

Index: src/platform-macos.cc
===================================================================
--- src/platform-macos.cc	(revision 1552)
+++ src/platform-macos.cc	(working copy)
@@ -593,6 +593,8 @@
   int Send(const char* data, int len) const;
   int Receive(char* data, int len) const;
 
+  bool SetReuseAddress(bool reuse_address);
+
   bool IsValid() const { return socket_ != -1; }
 
  private:
@@ -695,6 +697,13 @@
 }
 
 
+bool MacOSSocket::SetReuseAddress(bool reuse_address) {
+  int on = reuse_address ? 1 : 0;
+  int status = setsockopt(socket_, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
+  return status == 0;
+}
+
+
 bool Socket::Setup() {
   // Nothing to do on MacOS.
   return true;