building the gem.
* test/rubygems/test_gem_ext_ext_conf_builder.rb:  Test for the above.

* lib/rubygems/psych_tree.rb (module Gem):  Add backward compatibility
  for r41148

* test/rubygems/test_gem_package.rb:  Add backward compatibility for
  double-slash elimination.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41872 b2dd03c8-39d4-4d8f-98ff-823fe69b080e