gawk: Extension GMP/MPFR Versioning

 
 16.4.13.2 GMP and MPFR Version Information
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 The API also includes information about the versions of GMP and MPFR
 with which the running 'gawk' was compiled (if any).  They are included
 in the API 'struct' as read-only constant integers:
 
 'api->gmp_major_version'
      The major version of the GMP library used to compile 'gawk'.
 
 'api->gmp_minor_version'
      The minor version of the GMP library used to compile 'gawk'.
 
 'api->mpfr_major_version'
      The major version of the MPFR library used to compile 'gawk'.
 
 'api->mpfr_minor_version'
      The minor version of the MPFR library used to compile 'gawk'.
 
    These fields are set to zero if 'gawk' was compiled without MPFR
 support.
 
    You can check if the versions of MPFR and GMP that you are using
 match those of 'gawk' with the following macro:
 
 'check_mpfr_version(extension)'
      The 'extension' is the extension id passed to all the other macros
      and functions defined in 'gawkapi.h'.  If you have not included the
      '<mpfr.h>' header file, then this macro will be defined to do
      nothing.
 
      If you have included that file, then this macro compares the MPFR
      and GMP major and minor versions against those of the library you
      are compiling against.  If your libraries are newer than 'gawk''s,
      it produces a fatal error message.
 
      The 'dl_load_func()' macro (SeeExtension API Boilerplate)
      calls 'check_mpfr_version()'.