Add VeraCrypt support

These patches implement support for VeraCrypt (https://veracrypt.codeplex.com), a fork of TrueCrypt.
The first two patches are not related to VeraCrypt but are needed by the third patch which implement VeraCrypt support.

The first patch corrects the encoding of the minimum version field in the volume header.
The second patch brings a better handling of PRF algorithms by separating those used in system encryption from those used in standard containers encryption.
The third patch adds a switch ("veracrypt-mode") to tc-play that will activated VeraCrypt support in the used commands. The differences between normal mode and VeraCrypt mode are:
- PRF algorithms Iterations count (much higher than in TrueCrypt)
- SHA256 support for system encryption and in standard containers.
- value minimum version field in the volume header is 0x010b instead of 0x0700.
- Volume header signature is "VERA" instead of "TRUE"

VeraCrypt documentation that is derived from TrueCrypt one (without the mistakes): https://veracrypt.codeplex.com/documentation

Differences between VeraCrypt and TrueCrypt : https://veracrypt.codeplex.com/discussions/569777#PostContent_1313325