critical bugfix for asn1.x509.Certificate.sign()

• CRITICAL BUG FIX: KJUR.asn1.x509.Certificate.sign() and
  KJUR.asn1.x509.X509Util.newCertPEM() have always
  signed signatures with SHA1withRSA algorithm regardless
  of any specified signature algorithm. This issue was
  fixed in this release.
• asn1x509 1.0.19 to 1.0.20
  • Certificate
    • sign() critical bug fix
      sign() was always sign with SHA1withRSA regardless of
      specified any other signature algorithm.
      This fixes #240 and #241 by @helfloryd.
  • AlgorithmIdentifier
    • set algorithm parameter to NULL automatically by default
      for "*withRSA" algorithm.
    • document update
  • newCertPEM
    • fix document
• x509 1.1.11 to 1.1.12
  • X509.verifySignature static method added
• ext/rng.js
  • fix #228 from @dzaman. window.crypto.random fix
• crypto 1.1.11 to 1.1.12
  • minor document fix