maintainer-feedback requested: [Bug 271421] graphics/libfreehand: fix build with clang 16

Bugzilla Automation <bugzilla@FreeBSD.org> has asked FreeBSD Office Team
<office@FreeBSD.org> for maintainer-feedback:
Bug 271421: graphics/libfreehand: fix build with clang 16
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=271421



--- Description ---
Since clang 16 (and gcc 11) the default C++ standard is now gnu++17.
Because multimedia/smpeg's configure scripts and Makefiles do not
explicitly set the C++ standard, this leads to several errors:

  In file included from FreeHandDocument.cpp:14:
  In file included from ./FHParser.h:15:
  /usr/local/include/lcms2.h:1291:44: error: ISO C++17 does not allow
'register' storage class specifier [-Wregister]
  typedef cmsInt32Number (* cmsSAMPLER16)   (CMSREGISTER const cmsUInt16Number
In[],
					     ^~~~~~~~~~~~
  /usr/local/include/lcms2.h:158:23: note: expanded from macro 'CMSREGISTER'
  #  define CMSREGISTER register
			^
  /usr/local/include/lcms2.h:1292:44: error: ISO C++17 does not allow
'register' storage class specifier [-Wregister]
					     CMSREGISTER cmsUInt16Number Out[],
					     ^~~~~~~~~~~~
  /usr/local/include/lcms2.h:158:23: note: expanded from macro 'CMSREGISTER'
  #  define CMSREGISTER register
			^
  /usr/local/include/lcms2.h:1293:44: error: ISO C++17 does not allow
'register' storage class specifier [-Wregister]
					     CMSREGISTER void * Cargo);
					     ^~~~~~~~~~~~
  /usr/local/include/lcms2.h:158:23: note: expanded from macro 'CMSREGISTER'
  #  define CMSREGISTER register
			^
  /usr/local/include/lcms2.h:1295:44: error: ISO C++17 does not allow
'register' storage class specifier [-Wregister]
  typedef cmsInt32Number (* cmsSAMPLERFLOAT)(CMSREGISTER const cmsFloat32Number
In[],
					     ^~~~~~~~~~~~
  /usr/local/include/lcms2.h:158:23: note: expanded from macro 'CMSREGISTER'
  #  define CMSREGISTER register
			^
  /usr/local/include/lcms2.h:1296:44: error: ISO C++17 does not allow
'register' storage class specifier [-Wregister]
					     CMSREGISTER cmsFloat32Number
Out[],
					     ^~~~~~~~~~~~
  /usr/local/include/lcms2.h:158:23: note: expanded from macro 'CMSREGISTER'
  #  define CMSREGISTER register
			^
  /usr/local/include/lcms2.h:1297:44: error: ISO C++17 does not allow
'register' storage class specifier [-Wregister]
					     CMSREGISTER void * Cargo);
					     ^~~~~~~~~~~~
  /usr/local/include/lcms2.h:158:23: note: expanded from macro 'CMSREGISTER'
  #  define CMSREGISTER register
			^

Add -D CMS_NO_REGISTER_KEYWORD to CPPFLAGS, to avoid lcms2.h using
register keywords in its declarations.