Time#to_datetime breaks on master

Time#to_datetime breaks on master.

This works with 1.9.3:

$ ruby -v -rdate -e'p Time.new(2010, 10, 10).to_datetime'

This raises an exception with JRuby on master:

$ ../jruby/bin/jruby -v --1.9 -rdate -e'p Time.new(2010, 10, 10).to_datetime'

Here is my stack trace:

[aaron@mobile-166-129-194-155 psych (jruby)]$ ../jruby/bin/jruby -v --1.9 -rdate -e'p Time.new(2010, 10, 10).to_datetime'
jruby 1.7.0.dev (ruby-1.9.3-p203) (2012-04-27 69c9732) (Java HotSpot(TM) 64-Bit Server VM 1.6.0_31) [darwin-x86_64-java]
RubyTime$INVOKER$i$0$0$subsec.gen:-1:in `call': java.lang.NoSuchMethodError: org.jruby.RubyTime.subsec()Lorg/jruby/RubyRational;
from CachingCallSite.java:292:in `cacheAndCall'
from CachingCallSite.java:135:in `call'
from VCallNode.java:86:in `interpret'
from FCallTwoArgNode.java:38:in `interpret'
from CallOneArgNode.java:57:in `interpret'
from LocalAsgnNode.java:123:in `interpret'
from NewlineNode.java:104:in `interpret'
from BlockNode.java:71:in `interpret'
from ASTInterpreter.java:75:in `INTERPRET_METHOD'
from InterpretedMethod.java:147:in `call'
from DefaultMethod.java:183:in `call'
from CachingCallSite.java:292:in `cacheAndCall'
from CachingCallSite.java:135:in `call'
from -e:1:in `_file_'
from -e:-1:in `load'
from Ruby.java:778:in `runScript'
from Ruby.java:771:in `runScript'
from Ruby.java:648:in `runNormally'
from Ruby.java:497:in `runFromMain'
from Main.java:375:in `doRunFromMain'
from Main.java:264:in `internalRun'
from Main.java:230:in `run'
from Main.java:214:in `run'
from Main.java:194:in `main'
[aaron@mobile-166-129-194-155 psych (jruby)]$