Fix if/switch else after ceylon/ceylon-spec#74
Fix if/switch else after ceylon/ceylon-spec#74

When the type can be narrowed in an else clause (of an if or switch
statement), the grammar adds a synthetic variable to the else clause,
which includes the identifier of the value being switched on.
visitChildren() found this identifier, causing an unexpected token to be
written.

HenningB/ceylon.formatter