Fix cppcheck warnings.

src/async_worker.c

src/calendar.c

src/cdf_write.c

src/cdi_key.c

src/dmemory.c

src/extralib.c

src/file.c

src/getline.c

src/pio_client.c

src/pio_dbuffer.c

src/servicelib.c

src/stream_cdf_i.c

src/stream_cdf_o.c

src/stream_cgribex.c

src/stream_ieg.c

src/timebase.c

src/vlist.c

src/zaxis.c