improve coverage for gfuns

[ben-schwen]

Added testcases for increasing coverage of functions that are gforce optimized.

Also added two newlines decreasing coverage to be in line with PR #4299, although I'm not sure if we can really cover those.

[codecov]

Codecov Report

Merging #5192 (d8c5cf3) into master (5f9df4d) will increase coverage by 0.12%.
The diff coverage is 100.00%.

❗ Current head d8c5cf3 differs from pull request most recent head 230733d. Consider uploading reports for the commit 230733d to get more accurate results

@@            Coverage Diff             @@
##           master    #5192      +/-   ##
==========================================
+ Coverage   99.38%   99.51%   +0.12%     
==========================================
  Files          77       77              
  Lines       14532    14527       -5     
==========================================
+ Hits        14443    14456      +13     
+ Misses         89       71      -18     

Impacted Files	Coverage Δ
src/gsumm.c	100.00% <100.00%> (+2.33%)	⬆️

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[MichaelChirico]

I lean towards reverting the newlines there for now, while we still don't have any good answer to the point raised by Matt here:

#4301 (comment)

[ben-schwen]

I lean towards reverting the newlines there for now, while we still don't have any good answer to the point raised by Matt here:

#4301 (comment)

Perfect for me. I reverted now all newlines for if (nrow != n) to stay consistent.