Support discard option even for TCRYPT devices.
Support --tries option even for TCRYPT devices in cryptsetup.
Fix api test keyfile write.
Allow to use --disable-gcrypt-pbkdf2.

Unfortunately gcrypt PBKDF2 in libgcrypt 1.6.0 is very slow.
Until patch is accepted, let's allow switch back to internal kdf
implementation.

Fixes Issue#199, also see
https://bugzilla.redhat.com/show_bug.cgi?id=1051733
Add test for flawed Whirlpool hash to gcrypt backend.

Will be used later, for now add info to debug.
Ref: http://lists.gnupg.org/pipermail/gcrypt-devel/2014-January/002889.html
Do not use gcrypt KDF in 1.6.0, it is slow.

I hope 1.6.1 will have patch included (already in devel).
sync with Wiki-Version
Add --keep-key to cryptsetup-reencrypt.

This allows change of LUKS header hash (and iteration count) without
the need to reencrypt the whole data area.
Add internal shortcut for flawed whirlpool hash in gcrypt.