change precision EPSILON in C code

[ncourty]

Types of changes

• Docs change / refactoring / dependency upgrade
• [ X] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Motivation and context / Related issue

Problem INFEASIBLE cast where it should not happen.

Fixes #126

Fixes #93

How has this been tested (if it applies)

The minimal code to repdroduce the bug is now working.
A user tested on its own data and now the problem is also working

Checklist

• The documentation is up-to-date with the changes I made.
• I have read the CONTRIBUTING document.
• All tests passed, and additional code has been covered with new tests.

[codecov]

Codecov Report

Merging #217 (b554ebd) into master (93785eb) will increase coverage by 3.92%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #217      +/-   ##
==========================================
+ Coverage   88.48%   92.40%   +3.92%     
==========================================
  Files          20       16       -4     
  Lines        3196     3056     -140     
==========================================
- Hits         2828     2824       -4     
+ Misses        368      232     -136     

[ncourty]

Finally I only changed the final test value against EPSILON to test wether the problem is infeasible or not. It drastically limitates the side effects in the resolution of the problem.