dir.[ch]: remove PATH_MAX limitation

As discussed in [1], here's the first three patches of Duy's untracked cache series, which fixes a segfault with long paths on Windows.

[1] http://article.gmane.org/gmane.comp.version-control.msysgit/20702

Nguyễn Thái Ngọc Duy (3):
dir.c: coding style fix
dir.h: move struct exclude declaration to top level
prep_exclude: remove the artificial PATH_MAX limit

 dir.c | 59 ++++++++++++++++++++++++++++++++++-------------------------
 dir.h | 44 +++++++++++++++++++++++---------------------
 2 files changed, 57 insertions(+), 46 deletions(-)

2.0.0.9646.g840d1f9.dirty