Disambiguate the type name "complex"

[jamesjer]

When Fedora updated to GCC 15, the float package started failing to build if C-XSC support was included:

cxsc.C: In function 'OpaqueBag* CI_CXSC_STRING(Obj, Obj)':
cxsc.C:617:5: error: reference to 'complex' is ambiguous
  617 |     complex l, r;
      |     ^~~~~~~
In file included from /usr/include/c++/15/bits/stl_algobase.h:64,
                 from /usr/include/c++/15/string:53,
                 from /usr/include/cxsc/except.hpp:29,
                 from cxsc.C:68:
/usr/include/c++/15/bits/stl_pair.h:105:11: note: candidates are: 'template<class _Tp> class std::complex'
  105 |     class complex;
      |           ^~~~~~~
In file included from cxsc.C:70:
/usr/include/cxsc/complex.hpp:49:7: note:                 'class cxsc::complex'
   49 | class complex
      |       ^~~~~~~

This change disambiguates the type name complex, allowing the C-XSC interface to build successfully.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.45%. Comparing base (cf0ad14) to head (b52d2ef).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #101   +/-   ##
=======================================
  Coverage   54.45%   54.45%           
=======================================
  Files           6        6           
  Lines         942      942           
=======================================
  Hits          513      513           
  Misses        429      429           

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[fingolfin]

Ahh, bad luck / timing :-( @laurentbartholdi just made a release of float 2 hours before this PR sigh

[laurentbartholdi]

Ahh, bad luck / timing :-( @laurentbartholdi just made a release of float 2 hours before this PR sigh

I'm rightly punished for getting new releases out quickly. New version coming.

[fingolfin]

Thank you @laurentbartholdi !