LibGUI: Add GTCPSocket and base class GSocket (inherits from GIODevice.)

And use these to do the line-by-line reading automagically instead of having
that logic in IRCClient. This will definitely come in handy.

LibGUI/GSocket.cpp

@@ -0,0 +1,64 @@
+#include <LibGUI/GSocket.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <stdio.h>
+
+GSocket::GSocket(Type type, GObject* parent)
+    : GIODevice(parent)
+    , m_type(type)
+{
+}
+
+GSocket::~GSocket()
+{
+}
+
+bool GSocket::connect(const GSocketAddress& address, int port)
+{
+    ASSERT(!is_connected());
+    ASSERT(address.type() == GSocketAddress::Type::IPv4);
+    ASSERT(port > 0 && port <= 65535);
+
+    struct sockaddr_in addr;
+    memset(&addr, 0, sizeof(addr));
+    auto ipv4_address = address.ipv4_address();
+    memcpy(&addr.sin_addr.s_addr, &ipv4_address, sizeof(IPv4Address));
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(port);
+
+    printf("Connecting to %s...", address.to_string().characters());
+    fflush(stdout);
+    int rc = ::connect(fd(), (struct sockaddr*)&addr, sizeof(addr));
+    if (rc < 0) {
+        perror("connect");
+        exit(1);
+    }
+    printf("ok!\n");
+
+    m_destination_address = address;
+    m_destination_port = port;
+    m_connected = true;
+    return true;
+}
+
+ByteBuffer GSocket::receive(int max_size)
+{
+    auto buffer = read(max_size);
+    if (eof()) {
+        dbgprintf("GSocket{%p}: Connection appears to have closed in receive().\n", this);
+        m_connected = false;
+    }
+    return buffer;
+}
+
+bool GSocket::send(const ByteBuffer& data)
+{
+    int nsent = ::send(fd(), data.pointer(), data.size(), 0);
+    if (nsent < 0) {
+        set_error(nsent);
+        return false;
+    }
+    ASSERT(nsent == data.size());
+    return true;
+}