fixed IRB initialization in Ruby 1.8.7
fixed IRB initialization in Ruby 1.8.7

'irb' command blows up when debugger is started with
./script/server --debugger



git-svn-id: 88bbbf8f5798dc67c7e8670b837dd03176c2df4b@918 453b2852-3d18-0410-866e-d09c099698e4

gfowley/ruby-debug,gfowley/ruby-debug,ruby-debug/ruby-debug,ruby-debug/ruby-debug,ruby-debug/ruby-debug,gfowley/ruby-debug