Add doc/hacking to index
Update comments in mirrors.c for new methods
Add reduce method to built-in lists
Add methods to JS mirrors module to match native
Correct size of mgcollections sets
Add special case for StandardPrelude.new
Allow block information to be persisted to runtime

With this commit, the compiler (and dialects) can annotate a block with
an extra piece of information which will be available at runtime with
the extraRuntimeInformation method on the block. Where this annotation
was not given, this method does not exist.
Fix shadowing in logo_example