Add clang-format file

Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.

AK/Weakable.h

@@ -1,23 +1,29 @@
 #pragma once
 
 #include "Assertions.h"
-#include "Retainable.h"
 #include "RetainPtr.h"
+#include "Retainable.h"
 
 namespace AK {
 
-template<typename T> class Weakable;
-template<typename T> class WeakPtr;
+template<typename T>
+class Weakable;
+template<typename T>
+class WeakPtr;
 
 template<typename T>
 class WeakLink : public Retainable<WeakLink<T>> {
     friend class Weakable<T>;
+
 public:
     T* ptr() { return static_cast<T*>(m_ptr); }
     const T* ptr() const { return static_cast<const T*>(m_ptr); }
 
 private:
-    explicit WeakLink(T& weakable) : m_ptr(&weakable) { }
+    explicit WeakLink(T& weakable)
+        : m_ptr(&weakable)
+    {
+    }
     T* m_ptr;
 };
 
@@ -25,11 +31,12 @@ template<typename T>
 class Weakable {
 private:
     class Link;
+
 public:
     WeakPtr<T> make_weak_ptr();
 
 protected:
-    Weakable() { }
+    Weakable() {}
 
     ~Weakable()
     {