YAML file fails to load if JVM character set is MS932 (common on Windows)

I fail to load yaml file in windows7.

"InputStreamReader" is using "Charset.defaultCharset"
https://github.com/jruby/jruby/blob/master/core/src/main/java/org/jruby/ext/psych/PsychParser.java#L150
I expect that  this is causing the problem.

#### env
```
c:\workspace\yaml171>jruby -v
jruby 1.7.5.dev (1.9.3p392) 2013-09-09 f87088b on Java HotSpot(TM) Client VM 1.7.0_17-b02 [Windows 7-x86]
c:\workspace\yaml171>jruby -e "import java.nio.charset.Charset; p Charset.defaultCharset()"
#<Java::SunNioCsExt::MS932:0x181af25>
```

#### case
```ruby
#sample.rb

# -*- coding: utf-8 -*-
require 'yaml'
path = File.expand_path "../sample.yaml", __FILE__
p YAML.load_file(path)
```
```yml
# sample.yaml
ja:
  hoge: "テストほげ"
```

```
c:\workspace\yaml171>jruby sample.rb
Psych::SyntaxError: (c:/workspace/yaml171/sample.yaml): found unexpected end of stream while scanning a quoted scalar at line 3 column 1
         parse at org/jruby/ext/psych/PsychParser.java:212
  parse_stream at C:/workspace/sandbox/jruby/lib/ruby/shared/psych.rb:205
         parse at C:/workspace/sandbox/jruby/lib/ruby/shared/psych.rb:153
          load at C:/workspace/sandbox/jruby/lib/ruby/shared/psych.rb:129
     load_file at C:/workspace/sandbox/jruby/lib/ruby/shared/psych.rb:299
          open at org/jruby/RubyIO.java:1185
     load_file at C:/workspace/sandbox/jruby/lib/ruby/shared/psych.rb:299
        (root) at sample.rb:4
```