- It is now possible to add activity introduction voices.
	  If provided, it will be played when the activity starts and when
	  it's help is requested.
	  To provide an activity intro, you must put it under:
	  boards/voices/<locale>/activity/<activity name>-intro.ogg

	* configure.in: removed reference to cairo as goocanvas detects it
	* src/erase-activty/erase.c: (start_board), (end_board),
	(erase_one_item): moved the audio mode PLAY_AND_INTERRUPT only on
	the last item to avoid an intro voice to be cut.
	* src/gcompris/about.c: (gc_about_start): copyright is 2008 now.
	* src/gcompris/board.c: (gc_board_play): added support to play an
	optional intro voice a the start of an activity
	* src/gcompris/help.c: (gc_board_play): added support to play an
	optional intro voice when the help is lanched.
	* src/gcompris/bonus.c: (gc_bonus_display), (bonus_image):
	cleanup, removed extra warnings.
	* src/gcompris/gcompris.c: (cleanup), (single_instance_release),
	(single_instance_check): fixed the release of the lock when GC is exited.
	* src/gcompris/gameutil.c: (gc_activity_intro_play) created this function


svn path=/branches/gcomprixogoo/; revision=3312