stubdom: fix and clean pthread minimal support

diff -r f4a293cbec1b extras/mini-os/include/posix/pthread.h
@@ -1,18 +1,56 @@
 #ifndef _POSIX_PTHREAD_H
 #define _POSIX_PTHREAD_H
 
+#include <stdlib.h>
+
 /* Let's be single-threaded for now.  */
 
-typedef void *pthread_key_t;
-typedef struct {} pthread_mutex_t, pthread_once_t;
+typedef struct {
+    void *ptr;
+} *pthread_key_t;
+static inline int pthread_key_create(pthread_key_t *key, void (*destr_function)(void*))
+{
+    *key = malloc(sizeof(**key));
+    (*key)->ptr = NULL;
+    return 0;
+}
+static inline int pthread_setspecific(pthread_key_t key, const void *pointer)
+{
+    key->ptr = (void*) pointer;
+    return 0;
+}
+static inline void *pthread_getspecific(pthread_key_t key)
+{
+    return key->ptr;
+}
+static inline int pthread_key_delete(pthread_key_t key)
+{
+    free(key);
+    return 0;
+}
+
+
+
+typedef struct {} pthread_mutex_t;
 #define PTHREAD_MUTEX_INITIALIZER {}
-#define PTHREAD_ONCE_INIT {}
 static inline int pthread_mutex_lock(pthread_mutex_t *mutex) { return 0; }
 static inline int pthread_mutex_unlock(pthread_mutex_t *mutex) { return 0; }
-static inline int pthread_key_create(pthread_key_t *key, void (*destr_function)(void*)) { *key = NULL; return 0; }
-static inline int pthread_setspecific(pthread_key_t *key, const void *pointer) { *key = (void*) pointer; return 0; }
-static inline void *pthread_getspecific(pthread_key_t *key) { return *key; }
-static inline int pthread_once(pthread_once_t *once_control, void (*init_routine)(void)) { init_routine(); return 0; }
+
+
+
+typedef struct {
+    int done;
+} pthread_once_t;
+#define PTHREAD_ONCE_INIT { 0 }
+
+static inline int pthread_once(pthread_once_t *once_control, void (*init_routine)(void))
+{
+    if (!once_control->done) {
+        once_control->done = 1;
+        init_routine();
+    }
+    return 0;
+}
 
 #define __thread