pgsql: Make 8.3.x psql print tab characters as an appropriate number of

Log Message:
-----------
Make 8.3.x psql print tab characters as an appropriate number of spaces,
rather than "\x09". Before 8.3 we just printed tabs as-is, leading to poor
formatting of subsequent columns, but consensus is that "\x09" is not an
improvement over that. Back-patch of fix that's already in HEAD.

Tags:
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REL8_3_STABLE

Modified Files:
--------------
pgsql/src/bin/psql:
mbprint.c (r1.29 -> r1.29.2.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/mbprint.c?r1=1.29&r2=1.29.2.1)
mbprint.h (r1.11 -> r1.11.4.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/mbprint.h?r1=1.11&r2=1.11.4.1)
pgsql/src/test/regress/expected:
prepare.out (r1.15 -> r1.15.2.1)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/prepare.out?r1=1.15&r2=1.15.2.1)