Add explanation for new `from .. import class ..(..())` construct (see...

Add explanation for new `from .. import class ..(..())` construct (see clean-compiler-and-rts/compiler#4)

backend/Builtin/Syntax.icl

@@ -404,6 +404,11 @@ bs_import =
 		, "import code from \"tty.\"                // Import functions from the object file matching 'Clean System Files/tty.*'"
 		, "import code from library \"msvcrt\"      // Import functions from linked DLLs according to the msvcrt file in Clean System Files.\n" +
 		  "                                       // The file should start with the DLL name (e.g. msvcrt) and followed by one line per function you want to link."
+		] ++ map (add_imports ["StdEnv"] o EX)
+		[ "from StdMaybe import :: Maybe          // Import only the type Maybe"
+		, "from StdMaybe import :: Maybe(..)      // Import the type Maybe and all constructors"
+		, "from StdMaybe import :: Maybe(Just)    // Import the type Maybe and the Just constructor"
+		, "from Data.Foldable import class Foldable(foldr1()) // Import the class Foldable and the foldr1 member type"
 		] ++ map (requires_itask_compiler o EX)
 		[ "import qualified Data.Map as M         // Import Data.Map to use as e.g. 'M'.get (only supported by the iTask compiler)"
 		, "import Control.Monad => qualified join // Import Control.Monad except for join; join is imported qualified (only supported by the iTask compiler)"

backend/test/builtin_syntax.icl

@@ -129,7 +129,7 @@ where
 			i  -> trim (line % (0, i-1))
 		# doublecolon = indexOf "::" line
 		| doublecolon > 0
-				&& not (startsWith "generic " line || startsWith "class " line)
+				&& not (startsWith "generic " line || startsWith "class " line || startsWith "from " line)
 			// function without implementation
 			= case parseType [c \\ c <-: line & i <- [0..] | i > doublecolon+2] of
 				Just (Func is _ _) ->