* apt-pkg/acquire-item.{cc,h}:

* apt-pkg/acquire-item.{cc,h}:
  - rename "hash" into ExpectedHash in pkgAcqFile, pkgAcqIndex
  - add missing HashSum() call to class pkgAcqIndex
  - use the data provided by acquire-method (and send via the
    {SHA256,SHA1,MD5Sum}-Hash tag when comparing the hash, this
    avoids calculating the hash twice (just like old libapt)
* apt-pkg/acquire-method.cc:
  - send MD5Sum-Hash tag to libapt to be consistant with
    HashString::SupportedHashes()
* apt-pkg/acquire-worker.cc:
  - check with "Owner->HashSum().HashType()" what hash the frontend
    is expecting and pass it to pkgAcquireItem::Done() in the new
    HashString format
  - add some debugging output
* apt-pkg/contrib/hashes.cc:
  - fix off-by-one error when constructing a HashString from a single
    input string
* apt-pkg/contrib/hashes.h:
  - add "HashType()" method
* apt-pkg/init.h, apt-pkg/makefile, methods/makefile:
  - break ABI