Kernel: Move all code into the Kernel namespace

Kernel/Thread.cpp

@@ -28,6 +28,7 @@
 #include <AK/StringBuilder.h>
 #include <Kernel/Arch/i386/CPU.h>
 #include <Kernel/FileSystem/FileDescription.h>
+#include <Kernel/KSyms.h>
 #include <Kernel/Process.h>
 #include <Kernel/Profiling.h>
 #include <Kernel/Scheduler.h>
@@ -39,6 +40,8 @@
 //#define SIGNAL_DEBUG
 //#define THREAD_DEBUG
 
+namespace Kernel {
+
 static FPUState s_clean_fpu_state;
 
 u16 thread_specific_selector()
@@ -872,3 +875,5 @@ Thread* Thread::from_tid(int tid)
     });
     return found_thread;
 }
+
+}