Core: UnixSocket (AF_UNIX) implementation (#325)

* Core: UnixSocket (AF_UNIX) implementation

Core/UnixSocket: GetPeerPid refactored

reference/UnixSocketClient: Use default socket type for connection

reference/UnixSocketServer: Use default socket type for listen

Core: UnixSocket API docs & cleanup

Core: UnixSocket friend declaration guarded using ifdefs.

* Core: UnixSocket, GetPeerPid() refactored, docs updated

* Core: TcpSocket renamed as Socket and added unix domain socket support.
Cleanup
Updated API docs.

* Core: UnixSocket entry removed from API docs.

* Core: Socket/SocketWaitEvent API docs cosmetics.

* Core: Socket cosmetics

autotest/UnixSocket/UnixSocket.cpp

@@ -0,0 +1,51 @@
+#include <Core/Core.h>
+
+using namespace Upp;
+
+CONSOLE_APP_MAIN
+{
+#ifdef PLATFORM_POSIX
+
+	StdLogSetup(LOG_COUT|LOG_FILE);
+
+	String path = Format("/tmp/upp-unixsocket-test-%d", getpid());
+	
+	Socket server, client;
+	
+	// Test server listen
+	if(!server.ListenFileSystem(path)) {
+		LOG("Server listen failed: " << server.GetErrorDesc());
+		Exit(1);
+	}
+	
+	// Test client connect
+	if(!client.ConnectFileSystem(path)) {
+		LOG("Client connect failed: " << client.GetErrorDesc());
+		Exit(1);
+	}
+	
+	// Test data exchange
+	String test_data = "Hello, world!";
+	client.Put(test_data + "\n");
+	
+	Socket accepted;
+	if(!accepted.Accept(server)) {
+		LOG("Accept failed: " << accepted.GetErrorDesc());
+		Exit(1);
+	}
+	
+	String received = accepted.GetLine();
+	DUMP(received);
+	
+	ASSERT(received == test_data);
+	
+	// Test peer PID (on supported platforms)
+	int pid = accepted.GetPeerPid();
+	DUMP(pid);
+	if(pid != -1)
+		ASSERT(pid == getpid()); // Should be our own process in this test
+
+	LOG("=========== OK");
+
+#endif
+}

autotest/UnixSocket/UnixSocket.upp

@@ -0,0 +1,9 @@
+uses
+	Core;
+
+file
+	UnixSocket.cpp;
+
+mainconfig
+	"" = "";
+