initialisation of _Complex with an initializer list

[kroening]

Both gcc and clang allow the initialisation of C99 _Complex scalars with an initializer list of length two.

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[codecov]

Codecov Report

Attention: Patch coverage is 86.66667% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 77.94%. Comparing base (e6e665f) to head (0c1c1b3).

Files	Patch %	Lines
src/ansi-c/c_typecheck_initializer.cpp	86.66%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8265      +/-   ##
===========================================
- Coverage    77.95%   77.94%   -0.01%     
===========================================
  Files         1720     1720              
  Lines       189015   189030      +15     
  Branches     18402    18393       -9     
===========================================
- Hits        147346   147345       -1     
- Misses       41669    41685      +16     

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