pgsql: Remove ATPrepSetStatistics

Remove ATPrepSetStatistics

It was once possible to do ALTER TABLE ... SET STATISTICS on system
tables without allow_sytem_table_mods.  This was changed apparently by
accident between PostgreSQL 9.1 and 9.2, but a code comment still
claimed this was possible.  Without that functionality, having a
separate ATPrepSetStatistics() is useless, so use the generic
ATSimplePermissions() instead and move the remaining custom code into
ATExecSetStatistics().

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/cc8d2648-a0ec-7a86-13e5-db473484e19e%402ndquadrant.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/105eb360f2513523d221302b2d52880a14afae34

Modified Files
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src/backend/commands/tablecmds.c | 53 +++++++++-------------------------------
1 file changed, 12 insertions(+), 41 deletions(-)