first version of textlog with GUI

introducing generic "view" with two instantiations: stdout and textlist

common/utils/T/tracer/view/stdout.c

@@ -0,0 +1,35 @@
+#include "view.h"
+#include <stdlib.h>
+#include <stdio.h>
+#include <pthread.h>
+
+struct stdout {
+  view common;
+  pthread_mutex_t lock;
+};
+
+static void clear(view *this)
+{
+  /* do nothing */
+}
+
+static void append(view *_this, char *s)
+{
+  struct stdout *this = (struct stdout *)_this;
+  if (pthread_mutex_lock(&this->lock)) abort();
+  printf("%s\n", s);
+  if (pthread_mutex_unlock(&this->lock)) abort();
+}
+
+view *new_stdout(void)
+{
+  struct stdout *ret = calloc(1, sizeof(struct stdout));
+  if (ret == NULL) abort();
+
+  ret->common.clear = clear;
+  ret->common.append = (void (*)(view *, ...))append;
+
+  if (pthread_mutex_init(&ret->lock, NULL)) abort();
+
+  return (view *)ret;
+}