Port of Hasbrown #183 "Avoid closures to improve compile times"

[mucinoab]

This is the PR. I think I got everything in but let me know of any thoughts you may have.

[codecov-commenter]

Codecov Report

Merging #14 into master will decrease coverage by 0.19%.
The diff coverage is 77.27%.

Impacted Files	Coverage Δ
src/set.rs	59.23% <33.33%> (-1.44%)	⬇️
src/map.rs	68.29% <88.57%> (+0.57%)	⬆️
src/external_trait_impls/rayon/map.rs	81.37% <0.00%> (-0.69%)	⬇️
src/external_trait_impls/rayon/set.rs	99.07% <0.00%> (-0.47%)	⬇️
src/external_trait_impls/rayon/helpers.rs	100.00% <0.00%> (ø)
src/raw/mod.rs	73.42% <0.00%> (+0.45%)	⬆️

[jonhoo]

Ah, this is great, thank you! As long as you diff the code against the hashbrown code to make sure we match as closely as possible, it should be all good.

It also looks like you should do future changes based off of the newest griddle master branch. It appears you have some commits on your master branch that have probably been squashed on master :)