repo_haiku: get rid of haiku_version_to_string()

Use BPackageVersion::ToString() instead.
Haiku: The notation for the pre-release version part changed

Instead of using '-' as the separator for the pre-release '~' is used
now. This allows to drop code in a few places where Haiku had to be
special-cased before.
selection_filter(): Don't leak Queue q1 and Map m2
Merge pull request #29 from weinhold/upstream

Haiku pre-release version component separator changed