Lexer: Alternate Layout Rule injects actual not virtual braces

When the alternate layout rule is activated via a pragma, it injects tokens for { and } to make sure that the source is parsed properly.

But it injects ITocurly and ITccurly, rather than their virtual counterparts ITvocurly and ITvccurly.

This causes problems for ghc-exactprint, which tries to print these.

Test case (the existing T13087.hs)

{-# LANGUAGE AlternativeLayoutRule #-}
{-# LANGUAGE LambdaCase            #-}

isOne :: Int -> Bool
isOne = \case 1 -> True
              _ -> False

main = return ()

Trac metadata

Trac field	Value
Version	8.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Parser)
Test case
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