Shrink huffman decode tables

[folkertdev]

minor speedup for very small files

Benchmark 2 (745 runs): target/release/examples/decompress rs tests/input/bzip2-testfiles/go/crypto/SigVer.rsp.bz2
  measurement          mean ± σ            min … max           outliers         delta
  wall_time          6.68ms ±  143us    6.32ms … 7.28ms         29 ( 4%)        ⚡-  5.3% ±  0.2%
  peak_rss           3.08MB ± 66.5KB    2.88MB … 3.15MB          0 ( 0%)          -  0.1% ±  0.2%
  cpu_cycles         24.4M  ±  417K     23.9M  … 27.3M          57 ( 8%)        ⚡-  6.9% ±  0.1%
  instructions       55.7M  ±  305      55.7M  … 55.7M           4 ( 1%)        💩+  3.5% ±  0.0%
  cache_references    378K  ± 27.4K      293K  …  857K          26 ( 3%)          -  0.8% ±  0.6%
  cache_misses        102K  ± 2.02K     98.1K  …  111K           9 ( 1%)        ⚡-  2.3% ±  0.2%
  branch_misses       251K  ± 1.08K      250K  …  257K         134 (18%)        ⚡- 26.6% ±  0.0%

but for larger inputs it's not significant (makes sense)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ
libbz2-rs-sys/src/bzlib.rs	92.62% <ø> (ø)
libbz2-rs-sys/src/decompress.rs	93.42% <100.00%> (-0.11%)	⬇️
libbz2-rs-sys/src/huffman.rs	96.83% <100.00%> (+0.02%)	⬆️

[bjorn3]

u32::from(nextSym - 1)