pgsql: Index tuple data arrays using Anum_xxx symbolic constants instea

Index tuple data arrays using Anum_xxx symbolic constants instead of "i++".

We had already converted most places to this style, but this patch gets the
last few that were still doing it the old way. The main advantage is that
this exposes a greppable name for each target column, rather than having
to rely on comments (which a couple of places failed to provide anyhow).

Richard Hopkins, additional work by me to clean up update_attstats() too

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/bfcb9328e51eaaa21c92a1f2d7262758afb843e8

Modified Files
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src/backend/catalog/pg_operator.c | 58 ++++++++--------
src/backend/catalog/pg_type.c | 126 +++++++++++++++++------------------
src/backend/commands/analyze.c | 17 +++--
src/backend/commands/comment.c | 16 ++---
src/backend/rewrite/rewriteDefine.c | 18 ++---
5 files changed, 114 insertions(+), 121 deletions(-)