Mark tutorial as internal

[supertuxkart-sourceforge-migration]

Author: keewis

The tutorial is available in the track selection screen.

To solve this, set the "internal" attribute in data/tracks/tutorial/track.xml to "Y", as done in r11744 for "overworld".

Migrated-From: https://sourceforge.net/apps/trac/supertuxkart/ticket/884

[supertuxkart-sourceforge-migration]

Author: auria Done in r12494, thanks for the reminder!

[supertuxkart-sourceforge-migration]

Author: keewis thanks

there is a problem though: Error Could not load mesh, because file could not be opened: : .../data/tracks/overworld/crystal_ball_tuto.b3d irr_driver: Cannot load mesh <.../data/tracks/overworld/crystal_ball_tuto.b3d>

track: Object model '.../data/tracks/overworld/crystal_ball_tuto.b3d' not found, ignored.

Error Could not load mesh, because file could not be opened: : .../data/tracks/overworld//bubble_tuto.b3d irr_driver: Cannot load mesh <.../data/tracks/overworld//bubble_tuto.b3d>

Warning: object model '.../data/tracks/overworld//bubble_tuto.b3d' not found, ignored.

This results in a segfault in Track::convertTrackToBullet

[supertuxkart-sourceforge-migration]

Author: keewis sorry, the problem in my comment is not really related