Absolute value needed in stata code for rounding_4sigdig.do

[jrothbaumcensus]

replace var' = round(var',10^(floor(log10(`var'))-3))
should be:

replace var' = round(var',10^(floor(log10(abs(`var')))-3))

[simsong]

Neat. Can you submit a test vector which the original gets wrong and the correction gets right? Either here, or, better, as a pull request?