C binding of API

[godotalgorithm]

To make MOPAC more portable as a shared library, I have switched its new API to a C binding. This may be inconvenient to use in other Fortran-based software, so I also added a wrapper that re-implements the previous native Fortran API on top of the C binding.

Status

• Ready for merge

[codecov]

Codecov Report

Attention: Patch coverage is 76.64122% with 153 lines in your changes missing coverage. Please review.

Project coverage is 67.97%. Comparing base (b03d904) to head (cd0d325).
Report is 51 commits behind head on main.

Files with missing lines	Patch %	Lines
src/interface/mopac_api_createdestroy.F90	63.87%	56 Missing ⚠️
include/mopac_api_internal.F90	83.14%	45 Missing ⚠️
src/interface/mopac_api_finalize.F90	72.41%	16 Missing ⚠️
src/interface/mopac_api_operations.F90	33.33%	12 Missing ⚠️
src/MOZYME/iter_for_MOZYME.F90	0.00%	8 Missing ⚠️
src/interface/mopac_api_saveload.F90	86.44%	8 Missing ⚠️
src/interface/mopac_api_initialize.F90	84.21%	3 Missing ⚠️
src/run_mopac.F90	33.33%	2 Missing ⚠️
tests/mopac_api_test.F90	97.01%	2 Missing ⚠️
include/mopac_api_f.F90	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #218      +/-   ##
==========================================
+ Coverage   67.93%   67.97%   +0.04%     
==========================================
  Files         336      339       +3     
  Lines       77025    77421     +396     
==========================================
+ Hits        52326    52628     +302     
- Misses      24699    24793      +94     

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