Remove workaround

ceylon/ceylon-compiler#1492 was fixed, so the workaround is no longer
necessary.
source-gen: don’t garble documentation string

1. pass the documentation string as a verbatim string (triple quotes)
2. don’t discard empty lines (used in Markdown to separate paragraphs)
source-gen: support simple iterables as option types

For example, an option that contains the type ‘{Integer*}’ is parsed as

    { for (s in optionValue.split()) if (exists v=parseInteger(s)) v }

Union types in iterables are not supported yet.
Implement meta literals (reference expressions)

Things like `class Object` or `function print`
Add test for annotations with arguments + meta literals