Implement loggamma

[TSGut]

Moving progress over from JuliaMath/Bessels.jl#128

I also changed the name of the gamma.jl file to core.jl, happy for it to be renamed but gamma.jl and Gamma.jl causes namespace issues on some operating systems and we need Gamma.jl for the module. I will maybe do a few more commits to tidy this up, then it should be ready

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (a6ae907) to head (3c1b159).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main        #4      +/-   ##
===========================================
+ Coverage   98.76%   100.00%   +1.23%     
===========================================
  Files           2         3       +1     
  Lines          81       281     +200     
===========================================
+ Hits           80       281     +201     
+ Misses          1         0       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[TSGut]

@oscardssmith Ready for review.

[oscardssmith]

I'd like a different name than core. Maybe gamma_implimentation.jl?

[TSGut]

File renamed. 😄

[oscardssmith]

Thanks! Would be nice to have optimized lower precision versions, but this seems pretty good to start. If you don't object, I'll kick off the registration tonight/tomorrow.

[TSGut]

Happy for that to go ahead since I want to move my own work to use this instead soon.

I am also happy to revisit lower precision versions once that's done, I think it would just require looking into the right approximations to hard code in, similar to the current stuff.

[oscardssmith]

generally the low precision ones are easier since at the least, you can generally just cut a couple degrees off of the polynomial.