fixes for A2

mostly include some things that should and remove some things that shouldn't have been included in the handout (yes this does hint at some places that need to be touched for A2)

kernel/syscall/handler.cc

@@ -1,8 +1,6 @@
 #include "syscall/handler.h"
 
-#include "arch/core.h"
 #include "arch/core_interrupt.h"
-#include "arch/gdt.h"
 #include "arch/idt.h"
 #include "debug/kernelpanic.h"
 #include "debug/output.h"
@@ -26,12 +24,12 @@ namespace Syscall {
  * by the system call number -- allowing up to five parameters for the system
  * call.
  *
+ * \param sysnum identifier for the system call
  * \param p1 first parameter
  * \param p2 second parameter
  * \param p3 third parameter
  * \param p4 fourth parameter
  * \param p5 fifth parameter
- * \param sysnum identifier for the system call
  * \param user pointer to the interrupt \ref context (for example to determine
  * instruction pointer)
  * \return system call return value