TAUP not set to true zero

Because of the line “CALL OS('X=+(Y,C)', X=TAUP, Y=TAUP, C=ZERO)” in gaia_suspension_erode.f, TAUP is not exactly equal to zero when it should be, which can cause problems in bed1_suspension_erode (because TOCE_MIX can be 0 when there is no sediment mass).