pgsql: Modify canonicalize_path() so if we would return a trailing "..",

Log Message:
-----------
Modify canonicalize_path() so if we would return a trailing "..", throw
an error instead.

Modified Files:
--------------
pgsql/src/backend/postmaster:
postmaster.c (r1.464 -> r1.465)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c.diff?r1=1.464&r2=1.465)
pgsql/src/port:
Makefile (r1.25 -> r1.26)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/port/Makefile.diff?r1=1.25&r2=1.26)
path.c (r1.54 -> r1.55)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/port/path.c.diff?r1=1.54&r2=1.55)