* object.c (rb_obj_inspect): Kernel#inspect: do not call #to_s. A class
  can now benefit from the nice default #inspect even if it defines #to_s.
  Also, there is no more unexpected change in #inspect result.
* NEWS: Add note about the change.
* bignum.c, io.c, numeric.c, object.c, proc.c, vm.c (Init_*):
  Adapt internal structures (by aliasing #inspect to #to_s) so they
  don't rely on the removed behavior (#inspect calling overridden #to_s).
* test/ruby/test_object.rb (test_inspect): add tests for Kernel#inspect.
* lib/pp.rb (class PP): do not call #to_s anymore, as #inspect
  no more does (mame).
* test/test_pp.rb (class PPInspectTest): remove related assertion (mame).
  [ruby-core:43238][Feature #6130]
* test/drb/drbtest.rb (DRbCore#teardown, DRbAry#teardown):
  adapt DRb tests with the new change (shirosaki).
  [ruby-core:47182][Bug #6866]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36709 b2dd03c8-39d4-4d8f-98ff-823fe69b080e