RFC: Expose xnew in C_wrapper, maintaining compat

[odow]

Replacement for #313, just so I can try it out. I don't know if we should merge this. The alternative is for the user to write a closure, which isn't that much work.

cc @sohailrreddy

[codecov[bot]]

Codecov Report

Merging #322 (3ea2f8f) into master (e5f978c) will increase coverage by 0.27%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #322      +/-   ##
==========================================
+ Coverage   87.80%   88.07%   +0.27%     
==========================================
  Files           3        3              
  Lines         697      713      +16     
==========================================
+ Hits          612      628      +16     
  Misses         85       85              

Impacted Files	Coverage Δ
src/C_wrapper.jl	88.54% <100.00%> (+1.59%)	:arrow_up:

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[odow]

@sohailrreddy are you still interested in this? If not, I will close.

From https://github.com/jump-dev/Ipopt.jl/pull/313#issuecomment-1217459540:

I'd like to see a practical application where this makes a difference.

[odow]

Closing as stale. I understand the reasoning for this, so if anyone has a benchmark where this makes a difference in practice, please post a comment and we can re-open the PR.