unable to open more than 2 external files (thru 'open with' or doubleclick) on windows

[ciros88]

only two of them are actually added to the tracklist: the first and the last of all the selected ones.
works fine on both native linux and wine (the latter i suppose thanks to the bzr-player.sh file)

i've also noticed that, compared to the drag'n'drop action, when adding tracks from external open the playback begins for both (the first and the last), but it is so quick that the only last file playback is heard. this is suboptimal, playback should start only for the lats track. this difference in behaviors may also lead to #484 #524