kernel: various changes.

+ kernel: replace sk-hello test executable with a test initramfs
+ panic: start implementing a proper kernel panic screen
+ lib: added a new string.h library for string manipulation.
+ kernel: replace all the strlen implementations with the strlen() function

limine.conf

@@ -6,4 +6,4 @@ verbose: yes
     protocol: limine
 
     path: boot():/boot/soaplin
-    module_path: boot():/sk-hello.elf
+    module_path: boot():/initramfs.tar