* Cannot apply normal justice to FARC war - minister
* Says unrealistic to investigate, try all war crimes
* Correa says victims' voices will be heard
By Helen Murphy and Luis Jaime Acosta
BOGOTA, Sept 5 (Reuters) - Colombia's peace negotiations with Marxist FARC rebels will not lead to impunity for the rebels as critics fear after a half-century conflict that has killed more than 200,...