Implement GDT and basic IDT setup

This commit adds GDT initialization with proper code/data segments and reloads CS.

It also adds the initial IDT structure and loads an empty IDT.

Build configuration updated to disable SSE/MMX to prevent compiler generation of unsupported instructions in early boot.

README.md

@@ -42,6 +42,7 @@ Once a task is completed, it should be checked off.
 - [x] Setup a simple kernel that writes `Hello, world` to Qemu debug port
 - [x] Update the build system to create both ISO and Floppy images. Verify these work using a test script. The standard CMake build target should automatically generate both images. (Only ISO supported for now)
 - [ ] Update the kernel to correctly setup the GDT
+- [ ] Create an interrupt handler.
 - [ ] Create a physical memory allocator and mapper. The kernel should live in the upper last gigabyte of virtual memory. It should support different zones (e.g.: `SUB_16M`, `DEFAULT`, ...) These zones describe the region of memory that memory should be allocated in. If it is not possible to allocate in that region (because it is full, or has 0 capacity to begin with), it should fallback to another zone.
 - [ ] Create a paging subsystem. It should allow drivers to allocate and deallocate pages at will.
 - [ ] Create a memory allocator. This should provide the kernel with `malloc` and `free`. Internally, it should use the paging subsystem to ensure that the address it returns have actual RAM paged to them.