pgsql: Fold AlterForeignTableStmt into AlterTableStmt

Fold AlterForeignTableStmt into AlterTableStmt

All other relation types are handled by AlterTableStmt, so it's
unnecessary to make a different statement for foreign tables.

Discussion: https://www.postgresql.org/message-id/flat/163c00a5-f634-ca52-fc7c-0e53deda8735%402ndquadrant.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c4325cefba512772efc108baf8ef7182c3833716

Modified Files
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src/backend/parser/gram.y | 53 +++++++++++++++++++----------------------------
1 file changed, 21 insertions(+), 32 deletions(-)