C++ front-end: configure C++11+ syntax without ansi_c_parser object

[tautschnig]

There is no need to access the parser object when the same information is available directly from config.

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[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (1068770) 79.08% compared to head (a8d21c7) 79.08%.

Files	Patch %	Lines
src/cpp/parse.cpp	76.92%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8132   +/-   ##
========================================
  Coverage    79.08%   79.08%           
========================================
  Files         1696     1696           
  Lines       196505   196505           
========================================
  Hits        155408   155408           
  Misses       41097    41097           

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