Bump library version for v2.0.4

v2.0.3 release

v2.0.2 release

v2.0.1 release

v2.0.0 release

v1.0.6 release

v1.9.1 release

v1.9.0 release

make: Remove splint tests (ClusterLabs#374)

Now that splint is actually contradicting errors that come from
the compilers I think it's time to retire it. I could cope with it
being a minor nuisance on the argument that "another check can't
hurt", but contradicting the actual compilers is too much.

The CI has Coverity installed which is much more up-to-date anyway.
Splint hasn't been updated since 2010

v1.0.5 release