Fix construction from negative infinity binary floats

[mborland]

Closes: #1398

[codecov]

Codecov Report

❌ Patch coverage is 97.29730% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 98.4%. Comparing base (292399b) to head (0d99c84).
⚠️ Report is 5 commits behind head on develop.

Files with missing lines	Patch %	Lines
include/boost/decimal/decimal128_t.hpp	66.7%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #1399     +/-   ##
=========================================
- Coverage     98.4%   98.4%   -0.0%     
=========================================
  Files          290     291      +1     
  Lines        23499   23530     +31     
  Branches      2069    2069             
=========================================
+ Hits         23118   23147     +29     
- Misses         381     383      +2     

Files with missing lines	Coverage Δ
include/boost/decimal/decimal32_t.hpp	95.7% <100.0%> (+0.1%)	⬆️
include/boost/decimal/decimal64_t.hpp	95.0% <100.0%> (+0.1%)	⬆️
include/boost/decimal/decimal_fast128_t.hpp	95.7% <100.0%> (+0.1%)	⬆️
include/boost/decimal/decimal_fast32_t.hpp	97.5% <100.0%> (+0.1%)	⬆️
include/boost/decimal/decimal_fast64_t.hpp	97.6% <100.0%> (+0.1%)	⬆️
test/github_issue_1384.cpp	100.0% <ø> (ø)
test/github_issue_1398.cpp	100.0% <100.0%> (ø)
include/boost/decimal/decimal128_t.hpp	95.8% <66.7%> (-0.1%)	⬇️

... and 1 file with indirect coverage changes

---

Continue to review full report in Codecov by Harness.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 292399b...0d99c84. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.