fat_io_lib port WIP

kernel/libk/string.h

@@ -10,6 +10,7 @@ size_t strlen (const char* str);
 int memcmp (const void* s1, const void* s2, size_t n);
 int strncmp (const char* s1, const char* s2, size_t n);
 int strcmp (const char* s1, const char* s2);
+char* strncat (char* dest, const char* src, size_t n);
 
 #define strlen_null(x) (strlen ((x)) + 1)