pgsql-server: Allow relative paths as long as the hardcoded path matches

Log Message:
-----------
Allow relative paths as long as the hardcoded path matches the bin path
up to the last bin directory name.

Modified Files:
--------------
pgsql-server/src/port:
path.c (r1.14 -> r1.15)
(http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/port/path.c.diff?r1=1.14&r2=1.15)