distros.conf: enable DISTRO/updates along with DISTRO-backports

enable the security updates repository while installing backports
because backports may have been built against squeeze+security and
picked up bumped dependencies

Signed-off-by: Andreas Beckmann <anbe@debian.org>
lib/db: ensure initialization in public methods

always call _find_all_packages() or _compute_package_states()
before accessing lazy initialized structures

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-r,dwke,lib/db: add explicit compute_package_states()

this call must happen whit CWD == master-directory

Signed-off-by: Andreas Beckmann <anbe@debian.org>
lib/db: get_all_packages() returns a list, add get_all_package_names()

returning the dict was exposing an implementation detail

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p: fix perlism

Signed-off-by: Andreas Beckmann <anbe@debian.org>
detect_well_known_errors - Sort by bugged status first.
Change known_problem INCLUDE and EXCLUDE to PATTERN and EXCLUDE_PATTERN.
detect_well_known_errors - Validate known_problem field names.

Only load known problem configuration files with correct fields
defined.
Merge remote-tracking branch 'dave/issue-sort-fixes' into develop