Numbers are arbitrary, and we've never successfully made it to
version 1.0 after like 15 years or something.
Furthermore, plymouth has a very slow release schedule at present
and some distros hate building from git.
So, I'd like to start generating tarballs more regularly.
Adopting a version number derived from the date will help facilitate
that.
This commit changes AC_INIT to compute the version automatically.
https://gitlab.freedesktop.org/plymouth/plymouth/-/issues/143https://gitlab.freedesktop.org/plymouth/plymouth/-/issues/158
