small fixes
Fix errors/warnings in VS build

* Added libspeex to 'Debug' target, previously only 'Release' had it.
* Initialize some pointers with NULL when an uninitialized code path is
unlikely, but possible.
Fixes issues with colour drop down.
Started adding init_viewport
Fix compile error
Finished viewport_create for window_ride
Use new ride window when clicking on ride
Move cursor location fix #476
implement window_dropdown_show_colour
Fixes #482 caused by not passing the widgetIndex and x and y coordinates.
Added some checks on object loading to eventualy fix #225
Decompiled published credits window.

Renamed window_credits to window_music_credits.
Added draw_string_centred_underline to gfx.c.
start implementation of track list window
implement scrollmouseover and scrollpaint for track list window
implement track list window paint
implement window_track_list_select
implement track_get_info
implement sub_67726A, track loading function
add zoom touch gesture support
Add symbolic link if it is not present