Revert r28200.

It caused many failures on test-all and following is SEGV.
./ruby -e 'require %!#{"foo/" * 10000}foo!'

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@28245 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/custom_require.rb

@@ -4,6 +4,8 @@
 # See LICENSE.txt for permissions.
 #++
 
+require 'rubygems'
+
 module Kernel
 
   ##
@@ -29,17 +31,10 @@ module Kernel
     gem_original_require path
   rescue LoadError => load_error
     if load_error.message.end_with?(path) and
-        begin
-          Gem.try_activate(path)
-        rescue Gem::LoadError => load_error
-          pat = "#{__FILE__}:#{__LINE__-2}:in "
-          bt = load_error.backtrace
-          num = bt.index {|e| e.start_with?(pat)} and bt.shift(num+2)
-          raise load_error
-        end
-      retry
+       spec = Gem.searcher.find(path) then
+      Gem.activate(spec.name, "= #{spec.version}")
+      gem_original_require path
     else
-      load_error.backtrace.shift(2)
       raise load_error
     end
   end
@@ -47,5 +42,5 @@ module Kernel
   private :require
   private :gem_original_require
 
-end unless Kernel.private_method_defined?(:gem_original_require)
+end