trace fwrite-zlib on solaris

[mattdowle]

Closes #3931

Moved the malloc up before the parallel region. So that it can have its own more detailed error message and to avoid any concern about malloc thread safety on solaris 10.
Changed failed to bool and only write true, so it can be naked in the usual way.
Compress and write error codes separated explicitly. Probably overkill but to leave no doubt in case both positive and negative error codes are possible on Solaris, and to avoid needing to ask Prof Ripley to test a 2nd time.
The thread which fails and reaches ordered section first writes its error code thread-safely.

• sent to Prof Ripley to run on Solaris. Hopefully it will pass. If not, this should provide more detail on the error.
• remove temporary verbose just after test 1658.41

[mattdowle]

MacOS Travis has been running 27 mins so far. Frustrating. That's why it's off in dev. Linux finished in 10 mins.

[codecov]

Codecov Report

Merging #3954 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #3954      +/-   ##
=========================================
+ Coverage    99.4%   99.4%   +<.01%     
=========================================
  Files          72      72              
  Lines       13642   13648       +6     
=========================================
+ Hits        13561   13567       +6     
  Misses         81      81

Impacted Files	Coverage Δ
src/fwrite.c	97.86% <100%> (+0.02%)	⬆️

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