pgsql: Fix tablespace creation WAL replay to work on Windows.

Fix tablespace creation WAL replay to work on Windows.

The code segment that removes the old symlink (if present) wasn't clued
into the fact that on Windows, symlinks are junction points which have
to be removed with rmdir().

Backpatch to 9.0, where the failing code was introduced.

MauMau, reviewed by Muhammad Asif Naeem and Amit Kapila

Branch
------
REL9_3_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/84520f91ccec4d204ffae92af039544eb3541c39

Modified Files
--------------
src/backend/commands/tablespace.c |   33 +++++++++++++++++++++++++--------
1 file changed, 25 insertions(+), 8 deletions(-)