pgsql: Fix hard-coded relkind constants in assorted other files.

Fix hard-coded relkind constants in assorted other files.

Although it's reasonable to expect that most of these constants will
never change, that does not make it good programming style to hard-code
the value rather than using the RELKIND_FOO macros.

I think I've now gotten all the hard-coded references in C code.
Unfortunately there's no equally convenient way to parameterize
SQL files ...

Discussion: https://postgr.es/m/11145.1488931324@sss.pgh.pa.us

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/9c2635e26f6f4e34b3b606c0fc79d0e111953a74

Modified Files
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contrib/oid2name/oid2name.c | 17 ++++++++++++-----
contrib/postgres_fdw/postgres_fdw.c | 7 ++++++-
contrib/vacuumlo/vacuumlo.c | 4 +++-
src/backend/utils/adt/xml.c | 17 +++++++++++++++--
src/tools/findoidjoins/findoidjoins.c | 20 ++++++++++++--------
5 files changed, 48 insertions(+), 17 deletions(-)