Minor fix-ups for Darwin PowerPC

[barracuda156]

@ViralBShah This took forever :) Sorry for a ridiculous delay, it was forgotten.

Here are two tiny fixes:

1. Use a macro which includes ppc64, so that it is not left broken on macOS. (BTW, this still leaves out AIX, I believe?)
2. Make sure __BYTE_ORDER__ is actually defined: AFAIK, it may not be the case with some old gcc versions, and those support C99, so it is relevant.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 39.02%. Comparing base (4b83beb) to head (af8e580).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #303      +/-   ##
==========================================
+ Coverage   38.24%   39.02%   +0.78%     
==========================================
  Files         233      233              
  Lines        6139     6144       +5     
  Branches     1607     1608       +1     
==========================================
+ Hits         2348     2398      +50     
+ Misses       3394     3393       -1     
+ Partials      397      353      -44     

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[ViralBShah]

Windows is trying to use gcc instead of clang. Otherwise, happy to merge.

[barracuda156]

@ViralBShah Thanks for merging! This was super-fast.

[ViralBShah]

Would you like me to tag a new release?

[barracuda156]

Would you like me to tag a new release?

That would be certainly helpful, thank you.

[ViralBShah]

Released 0.8.3

[barracuda156]

Released 0.8.3

Updated in MacPorts in macports/macports-ports@9e47870