BRepositoryInfo: make sure fInitStatus is always set correctly
BRepositoryCache: use BStandardErrorOutput
BSolverRepository: fix gcc 4 build
BSolverRepository: add SetTo(const BRepositoryCache&)
pkgman: RepositoryBuilder: add BRepositoryCache c'tor
Repository file format: group attributes of a package

* Introduce new package attribute B_HPKG_ATTRIBUTE_ID_PACKAGE (valid
  only in a repository file) to group the attributes belonging to a
  package.
* BRepositoryContentHandler:
  - No longer derive from BPackageContentHandler.
  - Add hooks HandlePackage() and HandlePackageDone() that bracket the
    attributes for a package. This is more explicit and robust than
    handlers having to guess when one package ended and the next began.
* BRepositoryCache: Make use of BPackageInfoContentHandler. No need to
  duplicate the code for reading a package info from package info
  attributes.