Fix UTF-8 decoding problem in gf -server

The package network-2.4.1.1 thoughlessly introduced a backward incompatible
change to the function Network.URI.unEscapeString, see

    f2168b1f89

This also affects the function Network.Shed.Httpd.queryToArguments, which is
used in GFServer.hs.

To remain compatible with older and newer versions of the network package,
we need to stay clear of queryToArguments and unEscapeString. A replacement
function has been added to server/URLEncoding.hs.

src/compiler/GFServer.hs

@@ -24,8 +24,7 @@ import System.Posix.Files(getSymbolicLinkStatus,isSymbolicLink,removeLink,
 #endif
 import Control.Concurrent(newMVar,modifyMVar)
 import Network.URI(URI(..))
-import Network.Shed.Httpd(initServer,Request(..),Response(..),queryToArguments,
-                          noCache)
+import Network.Shed.Httpd(initServer,Request(..),Response(..),noCache)
 --import qualified Network.FastCGI as FCGI -- from hackage direct-fastcgi
 import Network.CGI(handleErrors,liftIO)
 import FastCGIUtils(handleCGIErrors)--,outputJSONP,stderrToFile
@@ -43,6 +42,7 @@ import Paths_gf(getDataDir,version)
 import GF.Infra.BuildInfo (buildInfo)
 import SimpleEditor.Convert(parseModule)
 import RunHTTP(cgiHandler)
+import URLEncoding(decodeQuery)
 
 --logFile :: FilePath
 --logFile = "pgf-error.log"
@@ -441,11 +441,17 @@ utf8inputs q = [(decodeString k,(decodeString v,v))|(k,v)<-inputs q]
 decoded = mapSnd fst
 raw = mapSnd snd
 
+inputs = decodeQuery
+{-
+-- Stay clear of queryToArgument, which uses unEscapeString, which had
+-- backward incompatible changes in network-2.4.1.1, see
+-- https://github.com/haskell/network/commit/f2168b1f8978b4ad9c504e545755f0795ac869ce
 inputs = queryToArguments . fixplus
   where
     fixplus = concatMap decode
     decode '+' = "%20" -- httpd-shed bug workaround
     decode c   = [c]
+-}
 
 mapFst f xys = [(f x,y)|(x,y)<-xys]
 mapSnd f xys = [(x,f y)|(x,y)<-xys]