CMD FOR with /d and Tilde functions shows uppercase incorrectly

The cmd:batch winetest shows failures with many tests because of a syntax like this:

for /d %%i in (.) do set WINE_CURDIR=%%~dpnxi

Currently some directories are changed to uppercase and this causes some tests to fail. The attached patch is an attempt to fix these failures. hbelusca, could you get us a tesbot run for this? Thanks.