BUG #4461: Should avoid create tblspcs in system location

The following bug has been logged online:

Bug reference: 4461
Logged by: Dmitry Orlov
Email address: dmitry_n_orlov(at)mail(dot)ru
PostgreSQL version: 8.3.3
Operating system: Ubuntu Hardy 8.04.1
Description: Should avoid create tblspcs in system location
Details:

if I issue create tablespace user_ts location
'/var/lib/postgresql/8.3/main/pg_tblspc' then appears nested links in
/var/lib/postgresql/8.3/main/pg_tblspc. So should avoid to create
tablespaces in pg_tblspc

postgres(at)dorlov-laptop:/home/dorlov/tmp/pgpool-II-2.1$ uname -a&&pg_config
Linux dorlov-laptop 2.6.24-19-rt #1 SMP PREEMPT RT Thu Aug 21 02:08:03 UTC
2008 i686 GNU/Linux
BINDIR = /usr/lib/postgresql/8.3/bin
DOCDIR = /usr/share/doc/postgresql-doc-8.3
INCLUDEDIR = /usr/include/postgresql
PKGINCLUDEDIR = /usr/include/postgresql
INCLUDEDIR-SERVER = /usr/include/postgresql/8.3/server
LIBDIR = /usr/lib
PKGLIBDIR = /usr/lib/postgresql/8.3/lib
LOCALEDIR = /usr/share/locale
MANDIR = /usr/share/postgresql/8.3/man
SHAREDIR = /usr/share/postgresql/8.3
SYSCONFDIR = /etc/postgresql-common
PGXS = /usr/lib/postgresql/8.3/lib/pgxs/src/makefiles/pgxs.mk
CONFIGURE = '--build=i486-linux-gnu' '--prefix=/usr'
'--includedir=/usr/include' '--mandir=/usr/share/man'
'--infodir=/usr/share/info' '--sysconfdir=/etc' '--localstatedir=/var'
'--libexecdir=/usr/lib/postgresql-8.3' '--disable-maintainer-mode'
'--disable-dependency-tracking' '--srcdir=.'
'--mandir=/usr/share/postgresql/8.3/man'
'--with-docdir=/usr/share/doc/postgresql-doc-8.3'
'--sysconfdir=/etc/postgresql-common' '--datadir=/usr/share/postgresql/8.3'
'--bindir=/usr/lib/postgresql/8.3/bin'
'--includedir=/usr/include/postgresql/' '--enable-nls'
'--enable-integer-datetimes' '--enable-thread-safety' '--enable-debug'
'--disable-rpath' '--with-tcl' '--with-perl' '--with-python' '--with-pam'
'--with-krb5' '--with-gssapi' '--with-openssl' '--with-libxml'
'--with-libxslt' '--with-ldap' '--with-ossp-uuid' '--with-gnu-ld'
'--with-tclconfig=/usr/lib/tcl8.4' '--with-tkconfig=/usr/lib/tk8.4'
'--with-includes=/usr/include/tcl8.4'
'--with-system-tzdata=/usr/share/zoneinfo' '--with-pgport=5432' 'CFLAGS=-g
-O2 -g -Wall -O2 -fPIC' 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,--as-needed'
'CC=cc' 'CPPFLAGS=' 'build_alias=i486-linux-gnu'
CC = cc
CPPFLAGS = -D_GNU_SOURCE -I/usr/include/libxml2 -I/usr/include/tcl8.4
CFLAGS = -g -O2 -g -Wall -O2 -fPIC -Wall -Wmissing-prototypes
-Wpointer-arith -Winline -Wdeclaration-after-statement -Wendif-labels
-fno-strict-aliasing -fwrapv -g
CFLAGS_SL = -fpic
LDFLAGS = -Wl,-Bsymbolic-functions -Wl,--as-needed
LDFLAGS_SL =
LIBS = -lpgport -lxslt -lxml2 -lpam -lssl -lcrypto -lkrb5 -lcom_err
-lgssapi_krb5 -lz -lreadline -lcrypt -ldl -lm
VERSION = PostgreSQL 8.3.3