SARAJEVO, April 19 (Reuters) - The most wanted man in the Balkans is being portrayed on the big screen this month as a vindictive army captain obsessed with gardening in a tragicomic film set during the dying days of Yugoslavia. Fugitive Bosnian Serb military chief Ratko Mladic, indicted for war crimes by the U.N. tribunal in The Hague, has been caricatured as Captain Rade Orchid in the film "Karaula" ("Border Post") by Croat director Rajko Grlic. The film has attracted attention across the Balkans as the first co-production by republics of the former socialist federation since its collapse in the...