Revert "stream: remove pointless & incomplete initialisation"

This reverts commit 830ea36e.

as requested in follow-up discussion in !1104.

(actually this is now a partial revert - the change to the return line has
been left in place per review request in !1193).

src/input/stream.c

@@ -74,12 +74,29 @@ stream_t *vlc_stream_CustomNew(vlc_object_t *parent,
     if (unlikely(priv == NULL))
         return NULL;
 
+    stream_t *s = &priv->stream;
+
+    s->psz_url = NULL;
+    s->psz_filepath = NULL;
+    s->s = NULL;
+    s->pf_read = NULL;
+    s->pf_block = NULL;
+    s->pf_readdir = NULL;
+    s->pf_seek = NULL;
+    s->pf_control = NULL;
+    s->p_sys = NULL;
+    s->p_input_item = NULL;
     assert(destroy != NULL);
     priv->destroy = destroy;
+    priv->block = NULL;
+    priv->peek = NULL;
+    priv->offset = 0;
+    priv->eof = false;
 
     /* UTF16 and UTF32 text file conversion */
     priv->text.conv = (vlc_iconv_t)(-1);
     priv->text.char_width = 1;
+    priv->text.little_endian = false;
 
     return &priv->stream;
 }