Bump ceylon.file version of source_gen module

The IDE was complaining that “source code” was importing both
ceylon.file 1.1.0 and 1.1.1. Not sure what that was about, but this
fixes it.
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.
Update for ceylon/ceylon-spec#74

Mostly just removing checks, but in one case I didn’t like how many
lines there were between the if and the else, so I turned it into a
switch instead so that you can see the type of the variable in the other
block as well.
Merge branch 'spec74'