dowild() does case insensitive matching by lower-casing the text. That
means lower case letters in patterns imply case-insensitive matching,
but upper case means exact matching.
We do not want that subtlety. Lower case pattern too so iwildmatch()
always does what we expect it to do.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>