Issue 174, 289: Update ICMP Specification

[rssen]

Closes #174
Fixes #289

[codecov]

Codecov Report

Merging #281 into develop will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #281      +/-   ##
===========================================
- Coverage    97.76%   97.74%   -0.02%     
===========================================
  Files           24       24              
  Lines         4074     4083       +9     
  Branches       674      678       +4     
===========================================
+ Hits          3983     3991       +8     
  Misses          52       52              
- Partials        39       40       +1     

Impacted Files	Coverage Δ
rflx/pyrflx/typevalue.py	99.25% <100.00%> (+0.01%)	⬆️
rflx/generator/generator.py	98.18% <0.00%> (-1.82%)	⬇️

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[rssen]

Apparently the test coverage for generator/generator.py went down but i did not make any changes to this module.

[treiher]

The dropped test coverage seems to be an bug of codecov. I think we can just ignore it here.

The ICMP specification looks fine for me now. But I don't like that you changed two unrelated things in one commit. Please split it and tag it with the right issue (Ref. #???).

This branch also needs to be rebased to develop.