Switch all open() calls to use g_open()

Because it now handles EINTR.  And we should do so.  While most people
use Linux, which tries very hard to avoid propagating EINTR back up
into userspace, it can still happen.

https://bugzilla.gnome.org/show_bug.cgi?id=682833

gio/tests/gdbus-peer.c

@@ -178,7 +178,7 @@ test_interface_method_call (GDBusConnection       *connection,
 
       error = NULL;
 
-      fd = open (path, O_RDONLY);
+      fd = g_open (path, O_RDONLY, 0);
       g_unix_fd_list_append (fd_list, fd, &error);
       g_assert_no_error (error);
       close (fd);

gio/tests/pollable.c

@@ -19,6 +19,7 @@
  */
 
 #include <gio/gio.h>
+#include <glib/gstdio.h>
 
 #ifdef G_OS_UNIX
 #include <fcntl.h>
@@ -154,7 +155,7 @@ test_pollable_unix (void)
   g_object_unref (out);
 
   /* Non-pipe/socket unix streams are not pollable */
-  fd = open ("/dev/null", O_RDWR);
+  fd = g_open ("/dev/null", O_RDWR, 0);
   g_assert_cmpint (fd, !=, -1);
   in = G_POLLABLE_INPUT_STREAM (g_unix_input_stream_new (fd, FALSE));
   out = g_unix_output_stream_new (fd, FALSE);