Libraries: Create top level directory for libraries.

Things were getting a little crowded in the project root, so this patch
moves the Lib*/ directories into Libraries/.

Libraries/LibC/serenity.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include <stdio.h>
+#include <unistd.h>
+
+#ifdef __cplusplus
+
+struct Stopwatch {
+    union SplitQword {
+        struct {
+            uint32_t lsw;
+            uint32_t msw;
+        };
+        uint64_t qw { 0 };
+    };
+
+public:
+    Stopwatch(const char* name)
+        : m_name(name)
+    {
+        read_tsc(&m_start.lsw, &m_start.msw);
+    }
+
+    ~Stopwatch()
+    {
+        SplitQword end;
+        read_tsc(&end.lsw, &end.msw);
+        uint64_t diff = end.qw - m_start.qw;
+        dbgprintf("Stopwatch(%s): %Q ticks\n", m_name, diff);
+    }
+
+private:
+    const char* m_name { nullptr };
+    SplitQword m_start;
+};
+
+#endif // __cplusplus