stackbuilder - wizard: Ensure we run as root on GTK platforms where

Log Message:
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Ensure we run as root on GTK platforms where installers generally cannot elevate their own privileges.

Modified Files:
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wizard:
StackBuilder.cpp (r1.10 -> r1.11)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/stackbuilder/wizard/StackBuilder.cpp.diff?r1=1.10&r2=1.11)