dialog: Fix dialog_admin documentation regarding column names.

(backport from b519d6997e6faa654ff4a513843359008f8cb66e)
Merge pull request #353 from wdoekes/wjd-dialog-modparam-columns-1.9

dialog: Fix dialog_admin documentation regarding column names.
Fix bogus unsigned to signed int conversion.

This leads to failures of computing VIA branches when hash label is higer than 2^31

(cherry picked from commit 2759890fcf41c1af1237206a0f97957cca1f635c)