pgsql: Add pgreadlink() on Windows to read junction points

Add pgreadlink() on Windows to read junction points

Add support for reading back information about the symbolic
links we've created with pgsymlink(), which are actually
Junction Points. Just like pgsymlink() can only create directory
symlinks, pgreadlink() can only read directory symlinks.

Branch
------
master

Details
-------
http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=db4d22d0eff091e96d92c82566c9e9d297040b93

Modified Files
--------------
src/include/port.h | 3 +
src/port/dirmod.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 121 insertions(+), 0 deletions(-)