msolve -V (and -h) to (also) print version

[dimpase]

With this,

   msolve -V

will print msolve's version, and

   msolve -h

will also print version, like

  msolve library for polynomial system solving, version 0.6.6

That's to be able to tell versions using msolve alone (without pkg-config, which is sometimes just absent, or misconfigured)

[dimpase]

@mezzarobba - to facilitate version reporting

[ederc]

Thanks.