ogma-core: Add import of Copilot's MTL module to Reqs DB translation.…

… Refs nasa#101.

The translation of FRET Requirement DBs to Copilot may produce specs that use
operators from the MTL module. However, that module is not being imported.

This commit modifies the translator from FRET Requirement DBs to Copilot so
that the MTL module is imported qualified.

ogma-core/src/Language/Trans/FRETReqsDB2Copilot.hs

@@ -112,6 +112,7 @@ fret2CopilotModule' prefs smvSpec cocoSpec = unlines $ concat sections
       , "import           Copilot.Library.PTLTL     (since, previous,"
         ++ " alwaysBeen)"
       , "import qualified Copilot.Library.PTLTL     as PTLTL"
+      , "import qualified Copilot.Library.MTL       as MTL"
       , "import           Language.Copilot          (reify)"
       , "import Prelude                   hiding ((&&), (||), (++), (<=), (>=),"
         ++ " (<), (>), (==), (/=), not)"