depqbf 1.0 - solver for quantified boolean formulas

http://lonsing.github.io/depqbf/

DepQBF is a search-based solver for quantified boolean formulae (QBF)
in prenex conjunctive normal form. It is based on the DPLL algorithm
for QBF, called QDPLL, with conflict-driven clause and solution-driven
cube learning.

Closes #19522.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>