changelog: change distribution

to allow scrips/make-changelog to not change existing entries

From the man page of git-dch: If the  distribution  of  the topmost section in debian/changelog is UNRELEASED the changelog entries will be inserted into this section. Otherwise a new section will be created.
changelog: missing v1.13 notes
changelog: remove duplicate entries
add sources to orig tarball
version 1.14
open for new development