BOGOTA, Feb 14 (Reuters) - Colombia, the world's fourth-largest coal exporter, produced 89.2 million tonnes of coal last year, missing its full-year target after problems with strikes and environmental permits bit into output, the government said on Thursday. Colombia's mining sector has been hit over the last year by a spate of labor disputes, including a strike at the main coal railway and a walkout at a Glencore-owned mine, as well as delays in environmental permits and a rise in guerrill