working dos vga writes!

Common/str.h

@@ -49,7 +49,7 @@ static inline int32_t com_str_ext_find_char(char const *s, char ch) {
 static inline bool com_str_ext_prefixed(char const *__restrict a,
                                         struct com_str const *prefix) {
   uint32_t n = prefix->len;
-  char *b = prefix->data;
+  char const *b = prefix->data;
   while (n && *a && (*a == *b)) {
     ++a;
     ++b;