Make code c++20 compliant

ChangeLog

src/async_worker.c

src/binary.h

src/cdf_filter.c

src/cdf_read.c

src/cdi_key.c

src/cdi_query.c

src/cgribexlib.c

src/grb_read.c

src/grb_write.c

src/gribapi_utilities.c

src/grid.c

src/iterator_fallback.c

src/stream_cdf_i.c

src/stream_cdf_o.c

src/stream_cgribex.c

src/stream_gribapi.c

src/stream_record.c

src/stream_write.c

src/subtype.c