Replaced UNDEFID by CDI_UNDEFID.

src/basetime.c

src/cdf_read.c

src/cdf_write.c

src/grid.c

src/institution.c

src/model.c

src/stream_cdf_i.c

src/stream_cdf_o.c

src/stream_ext.c

src/stream_ieg.c

src/stream_srv.c

src/table.c

src/varscan.c