Optimize impl From<i8> for LitBool

[hatoo]

master

❯ cargo clean && cargo build --release --features=unsafe && ./benchmark.sh target/release/screwsat 60
   Compiling screwsat v2.1.1 (/home/hatoo/fork/screwsat)
    Finished release [optimized + debuginfo] target(s) in 1.96s
Time Limit... 60 s
mkdir: cannot create directory ‘benchmark’: File exists
Solving.... cnf/benchmark/sat/grieu-vmpc-s05-24s.cnf
Status: SAT Time: 6480 ms
Solving.... cnf/benchmark/sat/stric-bmc-ibm-10.cnf
Status: SAT Time: 907 ms
Solving.... cnf/benchmark/sat/sudoku_16.cnf
Status: SAT Time: 66 ms
Solving.... cnf/benchmark/sat/uf250-027.cnf
Status: SAT Time: 1661 ms
Solving.... cnf/benchmark/sat/uf250-034.cnf
Status: SAT Time: 2741 ms
Solving.... cnf/benchmark/unsat/manol-pipe-f6b.cnf
Status: UNSAT Time: 2331 ms
Solving.... cnf/benchmark/unsat/uuf250-010.cnf
Status: UNSAT Time: 16049 ms
Solving.... cnf/benchmark/unsat/uuf250-0100.cnf
Status: UNSAT Time: 23335 ms
Solving.... cnf/benchmark/unsat/uuf250-032.cnf
Status: UNSAT Time: 17006 ms
Solving.... cnf/benchmark/unsat/uuf250-085.cnf
Status: UNSAT Time: 11906 ms
SAT: 5 UNSAT: 5 UNKNOWN: 0
Total Time: 82482 ms

this

❯ cargo clean && cargo build --release --features=unsafe && ./benchmark.sh target/release/screwsat 60
   Compiling screwsat v2.1.1 (/home/hatoo/fork/screwsat)
    Finished release [optimized + debuginfo] target(s) in 1.96s
Time Limit... 60 s
mkdir: cannot create directory ‘benchmark’: File exists
Solving.... cnf/benchmark/sat/grieu-vmpc-s05-24s.cnf
Status: SAT Time: 6867 ms
Solving.... cnf/benchmark/sat/stric-bmc-ibm-10.cnf
Status: SAT Time: 932 ms
Solving.... cnf/benchmark/sat/sudoku_16.cnf
Status: SAT Time: 66 ms
Solving.... cnf/benchmark/sat/uf250-027.cnf
Status: SAT Time: 1604 ms
Solving.... cnf/benchmark/sat/uf250-034.cnf
Status: SAT Time: 2549 ms
Solving.... cnf/benchmark/unsat/manol-pipe-f6b.cnf
Status: UNSAT Time: 2420 ms
Solving.... cnf/benchmark/unsat/uuf250-010.cnf
Status: UNSAT Time: 14750 ms
Solving.... cnf/benchmark/unsat/uuf250-0100.cnf
Status: UNSAT Time: 21409 ms
Solving.... cnf/benchmark/unsat/uuf250-032.cnf
Status: UNSAT Time: 15325 ms
Solving.... cnf/benchmark/unsat/uuf250-085.cnf
Status: UNSAT Time: 10881 ms
SAT: 5 UNSAT: 5 UNKNOWN: 0
Total Time: 76803 ms