Compile under windows

[stsci-hack]

Closes #
Resolves JP-nnnn

Description

This PR contains the simple changes to the C code necessary to allow the C extensions to compile under Windows. These changes swap out an indeterminate array definition with a redefinition using malloc to account for the varying size of the array for each dataset.

Checklist

• Tests
• Documentation
• Change log
• Milestone
• Label(s)

[codecov]

Codecov Report

Merging #6905 (7281c72) into master (64afee0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #6905   +/-   ##
=======================================
  Coverage   79.36%   79.36%           
=======================================
  Files         418      418           
  Lines       37343    37343           
=======================================
  Hits        29636    29636           
  Misses       7707     7707           

Flag	Coverage Δ		*Carryforward flag
nightly	79.34% <ø> (ø)		Carriedforward from 64afee0
unit	53.28% <ø> (ø)

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[pllim]

Is this all it takes for this package to run on Windows? Yes, please!

Would be nice to also add the Windows CI here, to be sure.