Remove defines_[defn|defs] flags from compiler

These flags are no longer used, and exact targets of these methods are
determined at runtime instead of being hardcoded to the compiler.
Name anonymous classes when assigning to a constant
Unexpectedly is "class variable"
Change Opal.dispatch_super to be just a super finder
Try to provide an implementation for process_defined with :colon2
Missing quotes
Indentation
Second attempt at defined? :colon2
It's lisp right?
Now we can raise safely
Add Kernel#respond_to_missing? along with #defined? support
One line's better
Regexp gvars ain't defined if nil
A more complete #defined? implementation for gvars
Catch just NameError for #defined? with colon2
Remove debugging output
Add the defined spec with failing (32) examples inside "bugs"
Merge pull request #401 from elia/fix-defined

Add the defined spec
Add Opal::Sexp instead of using Arrays for sexps
Remove last few edge cases still using arrays instead of sexps