Revert r36699 and r36700. [Feature #6130]

Revert "Kernel#inspect: improve consistency and do not call #to_s."
Revert "update PP with recent Kernel#inspect change. Patch by Yusuke Endoh."

r36699 cause test-all failure on test/drb/test_drb.rb and
test/drb/test_drbssl.rb. Run test-all before commit.

Moreover its ChangeLog formst is wrong: see CommitterHowto
https://bugs.ruby-lang.org/projects/ruby/wiki/CommitterHowto#ChangeLog

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36701 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/test_pp.rb

@@ -118,6 +118,7 @@ class PPInspectTest < Test::Unit::TestCase
     def a.to_s() "aaa" end
     result = PP.pp(a, '')
     assert_equal("#{a.inspect}\n", result)
+    assert_equal("aaa\n", result)
   end
 end