Add ET_DYN support for the ELF loader, which required adding

relocations, add some more functions to libxunil, use include inside of
tests instead of manually defining types and add basic libc header
files. Move libxunil to the user folder, and add helloworld and
doomgeneric as apps

user/libxunil/include/strings.h

@@ -0,0 +1,8 @@
+#pragma once
+#include <stddef.h>
+
+int    strcasecmp(const char *s1, const char *s2);
+int    strncasecmp(const char *s1, const char *s2, size_t n);
+void   bzero(void *s, size_t n);
+void   bcopy(const void *src, void *dest, size_t n);
+int    bcmp(const void *s1, const void *s2, size_t n);