Bump version requirements to base>=4.6, Cabal>=1.20

Cabal>=1.20 allows control over parallelism when compiling grammars from
Setup.hs and WebSetup.hs.

base>=4.6 allows conditional compilation with CPP to be eliminated from
a few modules.

base-4.6 corresponds to GHC 7.6.3, which is what you get in
Debian 8 (aka jessie, aka oldstable) from 2015.

WebSetup.hs

@@ -98,14 +98,13 @@ execute command args =
     showArg arg = if ' ' `elem` arg then "'" ++ arg ++ "'" else arg
 
 -- | This function is used to enable parallel compilation of the RGL and
--- example grammars, but it is commented out by default
--- to avoid casing problems for developers using Cabal<1.20
+-- example grammars
 numJobs flags =
     if null n
     then ["-j","+RTS","-A20M","-N","-RTS"]
     else ["-j="++n,"+RTS","-A20M","-N"++n,"-RTS"]
   where
     -- buildNumJobs is only available in Cabal>=1.20
-    n = {-case buildNumJobs flags of
+    n = case buildNumJobs flags of
           Flag mn | mn/=Just 1-> maybe "" show mn
-          _ ->-} ""
+          _ -> ""

gf.cabal

@@ -1,7 +1,7 @@
 name: gf
-version: 3.9
+version: 3.9-git
 
-cabal-version: >= 1.10
+cabal-version: >= 1.20
 build-type: Custom
 license: OtherLicense
 license-file: LICENSE
@@ -57,6 +57,7 @@ flag interrupt
 flag server
   Description: Include --server mode
   Default:     True
+
 flag network-uri
    description: Get Network.URI from the network-uri package
    default: True
@@ -68,6 +69,7 @@ flag network-uri
 flag custom-binary
   Description: Use a customised version of the binary package
   Default:     True
+  Manual:      True
 
 flag c-runtime
   Description: Include functionality from the C run-time library (which must be installed already)
@@ -75,7 +77,7 @@ flag c-runtime
 
 Library
   default-language:    Haskell2010
-  build-depends: base >= 4.5 && <5,
+  build-depends: base >= 4.6 && <5,
                  array,
                  containers,
                  bytestring,

src/compiler/GF/System/Catch.hs

@@ -1,13 +1,7 @@
--- | Isolate backwards incompatible library changes to 'catch' and 'try'
-{-# LANGUAGE CPP #-}
+-- | Backwards compatible 'catch' and 'try'
 module GF.System.Catch where
 import qualified System.IO.Error as S
 
 -- ** Backwards compatible try and catch
-#if MIN_VERSION_base(4,4,0)
 catch = S.catchIOError
 try = S.tryIOError
-#else
-catch = S.catch
-try = S.try
-#endif

src/compiler/GF/System/Concurrency.hs

@@ -1,7 +1,6 @@
-{-# LANGUAGE CPP,ForeignFunctionInterface #-}
+{-# LANGUAGE ForeignFunctionInterface #-}
 -- | A variant of 'Control.Concurrent.setNumCapabilities' that automatically
--- detects the number of processors in the system, and is available
--- even when compiling with GHC<7.6.
+-- detects the number of processors in the system.
 module GF.System.Concurrency(
   -- * Controlling parallelism
   setNumCapabilities,getNumberOfProcessors) where
@@ -16,13 +15,8 @@ import Foreign.C.Types(CInt(..))
 -- hasn't already been set with @+RTS -N/n/ -RTS@.
 setNumCapabilities opt_n =
   do n <- maybe getNumberOfProcessors return opt_n
-#if MIN_VERSION_base(4,6,0)
      C.setNumCapabilities n
      return True
-#else
-     n_now <- C.getNumCapabilities
-     return (n==n_now)
-#endif
 
 -- | Returns the number of processors in the system.
 getNumberOfProcessors = fmap fromEnum c_getNumberOfProcessors

src/runtime/haskell/PGF/Optimize.hs

@@ -1,4 +1,4 @@
-{-# LANGUAGE CPP, BangPatterns #-}
+{-# LANGUAGE BangPatterns #-}
 module PGF.Optimize
              ( optimizePGF
              , updateProductionIndices
@@ -11,11 +11,7 @@ import PGF.Macros
 import Data.List (mapAccumL)
 import Data.Array.IArray
 import Data.Array.MArray
-#if MIN_VERSION_base(4,6,0)
 import Data.Array.Unsafe as U(unsafeFreeze)
-#else
-import Data.Array.ST as U(unsafeFreeze)
-#endif
 import Data.Array.ST
 import Data.Array.Unboxed
 import qualified Data.Map as Map