Add support for long paths

* Add more file i/o wrappers in platform_utils to allow using
  long paths (length > MAX_PATH) on Windows.

* Paths using the long path syntax ("\\?\" prefix) should never
  escape the platform_utils API surface area, so that this
  specific syntax is not visible to the rest of the repo code base.

* Forward many calls from os.xxx to platform_utils.xxx in various place
  to ensure long paths support, specifically when repo decides to delete
  obsolete directories.

* There are more places that need to be converted to support long paths,
  this commit is an initial effort to unblock a few common use cases.

* Also, fix remove function to handle directory symlinks

Change-Id: If82ccc408e516e96ff7260be25f8fd2fe3f9571a

subcmds/status.py

@@ -26,6 +26,7 @@ import itertools
 import os
 
 from color import Coloring
+import platform_utils
 
 class Status(PagedCommand):
   common = True
@@ -115,7 +116,7 @@ the following meanings:
     """find 'dirs' that are present in 'proj_dirs_parents' but not in 'proj_dirs'"""
     status_header = ' --\t'
     for item in dirs:
-      if not os.path.isdir(item):
+      if not platform_utils.isdir(item):
         outstring.append(''.join([status_header, item]))
         continue
       if item in proj_dirs: