doc: add the :files option to specify additional, non-code, files
define_inherited_enumerable has been renamed to inherited_attribute
use ruby's malloc and free implementations as allocators in ValueSet

Otherwise, the allocations done by the set are not taken into
account to trigger the garbage collector, which can result in
very high memory consumption.
fix for Ruby 1.8
broke 1.9 while trying to fix 1.8. Proper fix for both versions.
add a threshold to ObjectStats.count_by_class
remove debugging output in RubyObjectGraph.dot_snapshot
fix the Proc extensions on Ruby 1.9.3
use the debugger-ruby_core_source gem to (optionally) get the internal headers needed by the Proc extensions
better warnings when the core sources are not available
fix linking of the extension on ruby 1.8
EventLoop: fix error handling when callback is not returning a symbol
add some accessor to event_loop and thread_pool
Fix: EventLoop.wait_for was accidentally terminating EventLoop.exec
thread_pool: better error reporting
define Logger#silent
logger: additional tests
event_loop: test errors against known error with is_a?
ext: display a message if the debugger core source gem is not available
ruby_object_graph: display the link between a class and its ancestors