Add subprocesses and convert terminal to an app

src/kernel/keyboard.c

@@ -50,11 +50,12 @@ static void append_sequence(const char *s) {
   }
 }
 
-static void stream_write(__attribute__((unused)) stream_t *self, __attribute__((unused)) const char *from,
-                         __attribute__((unused)) uint64_t size) {
+static uint64_t stream_write(__attribute__((unused)) const stream_t *self, __attribute__((unused)) const char *from,
+                             __attribute__((unused)) uint64_t bytes) {
+  return 0;
 }
 
-static uint64_t stream_read(__attribute__((unused)) stream_t *self, uint64_t max, char *to) {
+static uint64_t stream_read(__attribute__((unused)) const stream_t *self, uint64_t max, char *to) {
   if (max == 0 || buffer_length == 0) {
     return 0;
   }