Revert "dir.c: don't exclude whole dir prematurely if neg pattern may match"

Revert "dir.c: don't exclude whole dir prematurely if neg pattern may match"

This reverts commit 57534ee77d22e725d971ee89c77dc6aad61c573f. The
feature added in that commit requires that patterns behave the same way
from anywhere. But some patterns can behave differently depending on
current "working" directory. The conditions to catch and avoid these
patterns are too loose. The untracked listing[1] and sparse-checkout
selection[2] can become incorrect as a result.

  [1] http://article.gmane.org/gmane.comp.version-control.git/283520
  [2] http://article.gmane.org/gmane.comp.version-control.git/283532

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>