Fix/deduce endianness

[grisumbras]

Fix #717
Also see #576

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/719/pullrequest.html

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/719/pullrequest.html

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/719/pullrequest.html

[codecov]

Codecov Report

Merging #719 (b87b777) into develop (79700a1) will increase coverage by 0.04%.
The diff coverage is 100.00%.

❗ Current head b87b777 differs from pull request most recent head f1b9420. Consider uploading reports for the commit f1b9420 to get more accurate results

@@             Coverage Diff             @@
##           develop     #719      +/-   ##
===========================================
+ Coverage    99.08%   99.13%   +0.04%     
===========================================
  Files           69       69              
  Lines         6553     6552       -1     
===========================================
+ Hits          6493     6495       +2     
+ Misses          60       57       -3     

Impacted Files	Coverage Δ
include/boost/json/basic_parser_impl.hpp	99.20% <ø> (ø)
include/boost/json/detail/config.hpp	100.00% <ø> (ø)
include/boost/json/detail/sse2.hpp	97.77% <100.00%> (-0.02%)	⬇️
include/boost/json/detail/utf8.hpp	100.00% <100.00%> (+4.91%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 79700a1...f1b9420. Read the comment docs.

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/719/pullrequest.html

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/719/pullrequest.html

[vinniefalco]

Please no negative commit messages e.g. "confusing code." Instead express it as a positive "add clarifying implementation notes"

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/719/pullrequest.html