This adds a KFileItem constructor for passing a boolean
skipStat.changes the initialization of KFileItem. Constructors won't call init() which might do an unnecessary QT_LSTAT/stat() system call. Instead, only if a method which needs the information from stat() is called, If true,init() and stat() are run.
In addition this adds a KFileItem constructor for passing an enum MimeTypeDetermination parameter. KFileItemPrivate::init(),
KFileItem::determineMimeType() and KFileItem::currentMimeType()
won't callIf set to SkipMimeTypeDetermination,
KFileItem::determineMimeType(), KFileItem::currentMimeType() and KFileItem::iconName() won't call isDir(), QT_LSTAT or read the file.
See also https://phabricator.kde.org/D19784