ogma-core: Fix translation of equivalence boolean operator from SMV. …

…Refs #126.

The SMV to Copilot translator translates equivalences as (<==>).
However, that operator does not exist in Copilot; it is simply (==) for
Bools.

This commit replaces the translation of the equivalence operator from
SMV to be (==) in Copilot.

ogma-core/src/Language/Trans/SMV2Copilot.hs

@@ -83,7 +83,7 @@ boolSpec2Copilot b = case b of
                               ++ ")"
 
   BoolSpecEquivs spec1 spec2 -> "(" ++ boolSpec2Copilot spec1
-                             ++ " " ++ "<==>"
+                             ++ " " ++ "=="
                              ++ " " ++ boolSpec2Copilot spec2
                              ++ ")"