Merge branches 't/debian', 't/dynamic-lib', 't/lls_check_arg_count' and 't/news'

This octopus merge combines four branches, two of which were created
with the aim of making the package acceptable for inclusion into
Debian: The t/dynamic-lib branch instructs make to create a dynamic
library instead of the static one, the t/debian branch adds the usual
files below debian/.

The remaining two branches, t/lls_check_arg_count and t/news, contain
only a single commit each. The first improves the wording of an error
message while the second introduces the NEWS file, respectively.

The tree which corresponds to this commit was accepted for Debian
unstable on May 15 2019 as version 1.0.2-1.