The "helping" experimental strategy

[vorner]

Adds a new strategy. Also based on debt slots (modified hazard pointers), but doesn't fall back to the locking. The writers are lock-free too.

• Adds some miri tests too.

Closes #23 Relates to #34 and #8.

[codecov-io]

Codecov Report

Merging #48 (17769f2) into master (b45ec18) will decrease coverage by 1.19%. The diff coverage is 90.94%.

@@            Coverage Diff             @@
##           master      #48      +/-   ##
==========================================
- Coverage   90.13%   88.93%   -1.20%     
==========================================
  Files          14       15       +1     
  Lines         892     1157     +265     
==========================================
+ Hits          804     1029     +225     
- Misses         88      128      +40     

Impacted Files	Coverage Δ
src/strategy/rw_lock.rs	3.84% <0.00%> (ø)
src/weak.rs	83.33% <ø> (ø)
src/debt.rs	89.53% <60.00%> (-1.93%)	:arrow_down:
src/strategy/gen_lock.rs	92.30% <83.33%> (-3.35%)	:arrow_down:
src/strategy/helping.rs	85.83% <85.83%> (ø)
src/strategy/hybrid.rs	89.23% <87.50%> (-2.71%)	:arrow_down:
src/lib.rs	96.00% <96.49%> (+0.15%)	:arrow_up:
src/gen_lock.rs	84.90% <100.00%> (-1.89%)	:arrow_down:
tests/random.rs	100.00% <100.00%> (ø)
tests/stress.rs	93.96% <100.00%> (+0.10%)	:arrow_up:
... and 3 more