AK: Start fleshing out LogStream, a type-aware logging mechanism.

The first implementation class is DebugLogStream, which can be used like so:

    dbg() << "Hello friends, I am " << m_years << " years old!";

Note that it will automatically print a newline when the object created by
dbg() goes out of scope.

This API will grow and evolve, so let's see what we end up with :^)

AK/LogStream.h

@@ -0,0 +1,78 @@
+#pragma once
+
+#include <AK/AKString.h>
+#include <AK/StringView.h>
+#include <AK/kstdio.h>
+
+class LogStream {
+public:
+    LogStream() {}
+    virtual ~LogStream() {}
+
+    virtual void write(const char*, int) const = 0;
+};
+
+class DebugLogStream final : public LogStream {
+public:
+    DebugLogStream() {}
+    virtual ~DebugLogStream() override
+    {
+        char newline = '\n';
+        write(&newline, 1);
+    }
+
+    virtual void write(const char* characters, int length) const override
+    {
+        for (int i = 0; i < length; ++i)
+            dbgprintf("%c", characters[i]);
+    }
+};
+
+inline DebugLogStream dbg()
+{
+    return {};
+}
+
+inline const LogStream& operator<<(const LogStream& stream, const char* value)
+{
+    stream.write(value, strlen(value));
+    return stream;
+}
+
+inline const LogStream& operator<<(const LogStream& stream, const String& value)
+{
+    stream.write(value.characters(), value.length());
+    return stream;
+}
+
+inline const LogStream& operator<<(const LogStream& stream, const StringView& value)
+{
+    stream.write(value.characters(), value.length());
+    return stream;
+}
+
+inline const LogStream& operator<<(const LogStream& stream, char value)
+{
+    stream.write(&value, 1);
+    return stream;
+}
+
+inline const LogStream& operator<<(const LogStream& stream, bool value)
+{
+    return stream << (value ? "true" : "false");
+}
+
+inline const LogStream& operator<<(const LogStream& stream, int value)
+{
+    return stream << String::number(value);
+}
+
+inline const LogStream& operator<<(const LogStream& stream, unsigned value)
+{
+    return stream << String::number(value);
+}
+
+inline const LogStream& operator<<(const LogStream& stream, const void* value)
+{
+    return stream << String::format("%p", value);
+}