Implemented Higher Half Kernel!

- Minor makefile chnages
- stage3.c "prekernel", sets up memory stuff and jumps to kernel
- kernel is now at 0xC0000000 - 3GB+ "higher half"
- Added some global variables in memory/addresses.h

src/kernel.ld

@@ -1,5 +1,5 @@
 SECTIONS {
-    .text 0x50000 : {
+    .text 0xC0000000 : {
         *(entry);
         *(.text*);
     }