LibCore: Add CThread, a simple thread abstraction object.

Currently this is only a simple wrapper around create_thread() that
remembers the thread ID of the spawned thread.

Libraries/LibCore/CThread.cpp

@@ -0,0 +1,29 @@
+#include <AK/Assertions.h>
+#include <LibCore/CEventLoop.h>
+#include <LibCore/CThread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+CThread& CThread::main_thread()
+{
+    static CThread* main_thread;
+    if (!main_thread)
+        main_thread = new CThread(MainThread);
+    return *main_thread;
+}
+
+CThread::CThread(MainThreadTag)
+    : m_thread_id(0)
+{
+}
+
+CThread::CThread(int (*entry)(void*), void* user_data)
+{
+    ASSERT(entry);
+    m_thread_id = create_thread(entry, user_data);
+}
+
+CThread::~CThread()
+{
+}