Revert r29986: "Imported minitest 2.0.0 r5952"

This breaks test-all:
* two test-all errors (test_run_passing and test_run_failing_filtered).
* -v option to test-all is ignored

Additional to say, please describe summary of the change when you
import from external repository.

And, RUN test-all BEFORE COMMIT.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29988 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/minitest/spec.rb

@@ -66,13 +66,10 @@ module Kernel
 
   def describe desc, &block
     stack = MiniTest::Spec.describe_stack
-    name  = [stack.last, desc].compact.join("::")
-    cls   = Class.new(stack.last || MiniTest::Spec)
-
-    # :stopdoc:
-    # omg this sucks
-    (class << cls; self; end).send(:define_method, :to_s) { name }
-    # :startdoc:
+    name  = desc.to_s.split(/\W+/).map { |s| s.capitalize }.join + "Spec"
+    prev  = stack.last
+    name  = "#{prev == MiniTest::Spec ? nil : prev}::#{name}"
+    cls   = Object.class_eval "class #{name} < #{prev}; end; #{name}"
 
     cls.nuke_test_methods!
 
@@ -99,7 +96,7 @@ end
 
 
 class MiniTest::Spec < MiniTest::Unit::TestCase
-  @@describe_stack = []
+  @@describe_stack = [MiniTest::Spec]
   def self.describe_stack # :nodoc:
     @@describe_stack
   end