Initial change to permit use of inline template haskell, to address

issue: https://github.com/gibiansky/IHaskell/issues/236

To verify functionality, paste the following into a code block in
IHaskell.

```
:ext TemplateHaskell
import Language.Haskell.TH
import Control.Lens
data Foo a = Foo { _bar :: Int, _baz :: Int, _quux :: a }
makeLenses ''Foo
:ty baz
```

ihaskell.cabal

@@ -85,6 +85,7 @@ library
                        system-argv0         -any,
                        system-filepath      -any,
                        tar                  -any,
+                       template-haskell     -any, 
                        text                 >=0.11,
                        transformers         -any,
                        unix                 >= 2.6,

src/IHaskell/Eval/Evaluate.hs

@@ -20,6 +20,7 @@ import Data.Char as Char
 import Data.Dynamic
 import Data.Typeable
 import qualified Data.Serialize as Serialize
+import qualified Language.Haskell.TH as TH  
 import System.Directory
 import Filesystem.Path.CurrentOS (encodeString)
 import System.Posix.IO
@@ -78,7 +79,7 @@ data ErrorOccurred = Success | Failure deriving (Show, Eq)
 
 -- | Enable debugging output
 debug :: Bool
-debug = False
+debug = False  
 
 -- | Set GHC's verbosity for debugging
 ghcVerbosity :: Maybe Int
@@ -704,8 +705,20 @@ evalCommand output (Expression expr) state = do
   let widgetExpr = printf "(IHaskell.Display.Widget (%s))" expr :: String
   isWidget <- attempt $ exprType widgetExpr
 
+  -- Check if this is a declaration  
+ -- let declExpr = printf "((id :: Q [Dec] -> Q [Dec]) (%s))" expr::String
+  let declExpr = printf "((id :: DecsQ -> DecsQ) (%s))" expr::String
+  isDeclaration <- attempt $ exprType declExpr  
+
   write $ "Can Display: " ++ show canRunDisplay
-  write $ "  Is Widget: " ++ show canRunDisplay
+  write $ "  Is Widget: " ++ show isWidget 
+  if isDeclaration 
+  then do 
+      write $ "  Is Declaration: " ++ show isDeclaration 
+      (GHC.runDecls expr) >> return ()  
+  else  
+      write $ "  Is Declaration:" ++ show isDeclaration 
+
 
   if canRunDisplay
   then do
@@ -716,20 +729,31 @@ evalCommand output (Expression expr) state = do
     if isWidget
     then registerWidget out
     else return out
-
   else do
-    -- Evaluate this expression as though it's just a statement.
-    -- The output is bound to 'it', so we can then use it.
-    evalOut <- evalCommand output (Statement expr) state
-
-    let out = evalResult evalOut
-        showErr = isShowError out
-
-    -- If evaluation failed, return the failure.  If it was successful, we
-    -- may be able to use the IHaskellDisplay typeclass.
-    return $ if not showErr || useShowErrors state
-            then evalOut
-            else postprocessShowError evalOut
+    if isDeclaration 
+    -- We do not want to display the DecsQ, we just want the 
+    -- declaration made. 
+    then do write $ "Suppressing display for template haskell declaration"  
+            return EvalOut {
+                    evalStatus = Success,
+                    evalResult = mempty,  
+                    evalState = state,
+                    evalPager = "",
+                    evalComms = []
+                }
+    else do  
+            -- Evaluate this expression as though it's just a statement.
+            -- The output is bound to 'it', so we can then use it.
+            evalOut <- evalCommand output (Statement expr) state
+
+            let out = evalResult evalOut
+                showErr = isShowError out
+
+            -- If evaluation failed, return the failure.  If it was successful, we
+            -- may be able to use the IHaskellDisplay typeclass.
+            return $ if not showErr || useShowErrors state
+                    then evalOut
+                    else postprocessShowError evalOut
 
   where
     -- Try to evaluate an action. Return True if it succeeds and False if