textproc/groff: fix build with clang 16
Since clang 16 (and gcc 11) the default C++ standard is now gnu++17.
Because textproc/groff's Makefile does not explicitly set its C++
standard, this leads to several errors:
src/preproc/grn/hdb.cpp:38:15: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
int DBGetType(register char *s);
^~~~~~~~~
src/preproc/grn/hdb.cpp:64:3: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
register ELT *temp;
^~~~~~~~~
src/preproc/grn/hdb.cpp:83:8: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
DBRead(register FILE *file)
^~~~~~~~~
src/preproc/grn/hdb.cpp:85:3: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
register int i;
^~~~~~~~~
src/preproc/grn/hdb.cpp:86:3: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
register int done; /* flag for input exhausted */
^~~~~~~~~
src/preproc/grn/hdb.cpp:87:3: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
register double nx; /* x holder so x is not set before orienting */
^~~~~~~~~
src/preproc/grn/hdb.cpp:212:11: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
DBGetType(register char *s)
^~~~~~~~~Add USE_CXXSTD=gnu++98 to avoid these errors.
Approved by: bapt (maintainer)
MFH: 2023Q2