Renames the current version function and define to dav1d_version_vcs()
and DAV1D_VERSION_VCS. Fixes #241.
The generated version.h is included as "dav1d/version.h" to avoid errors
with a stale include/version.h in a build dir.

This is similar to --noblit of libaom

Marvin Scholz authored Oct 01, 2018 and Jean-Baptiste Kempf committed Oct 02, 2018

Due to bugs in meson the approach with the intermediate static library
for tests does not work very well, see #44. Therefore this commits
removes that helper library and instead uses extract_all_objects for
the tests.

Due to the removal of the static helper library, it means we can no
longer force static linking for dav1d tool on windows which means that
when building a shared library the dav1d.exe will not be runnable in
the build directory again.

Fix #44