user32: Check for bad scroll value and fix return values in EDIT_EM_Scroll

[Austin English]

Based on a patch by David Hedberg. Rediffed against current git. Fixes bug 1517.
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: 0001-user32-Check-for-bad-scroll-value-and-fix-return-va.txt
Url: http://www.winehq.org/pipermail/wine-patches/attachments/20080804/cd6088bc/attachment.txt