version with 2020 competition solver features

version submitted to SAT Race 2019

coverity: track master

version 2.2.0 of minisat.se

http://minisat.se/downloads/minisat-2.2.0.tar.gz

Merge branch 'msoos-master'

Merge pull request conp-solutions#1 from Robbepop/master

fixed GCC 6.3 warning: invalid suffix on literal; C++11 requires a sp…

Remove a file that is not used in main branch.

Import of version 2.0.