st: Minor updates to -estout- and -mrtab- on SSC

["Jann, Ben" <ben.jann@soz.gess.ethz.ch>]

Thanks to Kit Baum, the -estout- and -mrtab- packages have
been updated on SSC.

Only minor changes have been made:

-estout- now issues an error message if an unknown suboption
is used in the -cells()- option.

mrtab.ado contained misleading release information. This is
fixed.

ben


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