Interrupts are now working.

GDT:
*Fixed the argument sizes in gdt.c declaration of the Assembly symbol. The
second argument (which is the size) is now a unsigned 16 bit integer.

IDT:
*Rewritten based on the GDT module (that i know worked).
*Tested with IRQ 0 (division by 0 exception) and it works fine.

Kernel:
*Added a 'naked' interrupt function for testing that prints a message
on the screen when it is called
*It now loads the IDT and adds an ISR on the 0 exception (division by 0).
After that it tests it by performing 15/0. The ISR gets called successfuly.

Makefile:
*Changed the compiler from GCC to Clang as it supports the 'naked' attribute for
functions (needed for ISR functions).