we always should load ruby-debug-base for JRuby

this change fix first problem we have with debugging JRuby with language level 2.0.
But after that I've got the following exception which means ruby-debug-base should also be patched for this language level.
Util.java:122:in `typeForEvent': java.lang.IllegalArgumentException: unknown event type: b-return
	from DebugEventHook.java:97:in `eventHandler'
	from EventHook.java:30:in `event'
	from Ruby.java:2882:in `callEventHooks'
	from ThreadContext.java:629:in `trace'
	from ThreadContext.java:625:in `trace'
	from ASTInterpreter.java:140:in `blockPostTrace'
	from ASTInterpreter.java:114:in `INTERPRET_BLOCK'
	from Interpreted19Block.java:206:in `evalBlockBody'
	from Interpreted19Block.java:194:in `yield'
	from Interpreted19Block.java:125:in `call'
	from Block.java:101:in `call'
	from RubyProc.java:274:in `call'
	from RubyProc.java:215:in `call'
	from Ruby.java:2973:in `tearDown'
	from Ruby.java:2957:in `tearDown'
	from Main.java:282:in `internalRun'
	from Main.java:221:in `run'
	from Main.java:201:in `main'