pgsql: Activate WIN32_STACK_RLIMIT override only on platforms where this

Log Message:
-----------
Activate WIN32_STACK_RLIMIT override only on platforms where this is
necessary.

Modified Files:
--------------
pgsql/src/backend/tcop:
Makefile (r1.26 -> r1.27)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/Makefile.diff?r1=1.26&r2=1.27)