pgpool: Fix duplicate NodeTag enum in nodes.h.

Fix duplicate NodeTag enum in nodes.h.

The file was imported from PostgreSQL and Pgpool-II specific node type
were added right after T_Invalid = 0, then nodetags.h is
included. Since nodetags.h explicitly assign values to each enum
starting from 1, and this created duplicated enums.
T_List = 1,
T_Alias = 2,
T_RangeVar = 3,
T_PgpoolVariableSetStmt, (1)
T_PgpoolVariableShowStmt, (2)
T_PgpoolQueryCacheStmt, (3)

Although fortunately this seems does not create any trouble except the
duplicated enums, this should be fixed: moving the inclusion of
nodetags.h right after "T_invalid = 0".

Reported-by: liujinyang-highgo
Diagnosed-by: liujinyang-highgo
Discussion: https://github.com/pgpool/pgpool2/issues/138
Backpatch-through: v4.5

Branch
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V4_5_STABLE

Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=6e4f664a5c2e4961029eada15258a7a118096f39

Modified Files
--------------
src/include/parser/nodes.h | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)