Fix compatibility wiht Bouncy Castle 1.49.

Hi,

I am trying to update JRuby packages in Fedora and it seems that JRuby is not compatible with Bouncy Castle 1.49:

```
[ERROR] /builddir/build/BUILD/jruby-1.7.5/ext/openssl/src/main/java/org/jruby/ext/openssl/x509store/PEMInputOutput.java:[369,36] error: PBES2Parameters(ASN1Sequence) has private access in PBES2Parameters
[ERROR] /builddir/build/BUILD/jruby-1.7.5/ext/openssl/src/main/java/org/jruby/ext/openssl/x509store/PEMInputOutput.java:[375,89] error: cannot find symbol
[ERROR] /builddir/build/BUILD/jruby-1.7.5/ext/openssl/src/main/java/org/jruby/ext/openssl/x509store/PEMInputOutput.java:[381,49] error: cannot find symbol
```

I come with this patch to fix the compatibility. I would appreciate if you can accept