pgsql: Tighten ALTER FOREIGN TABLE .. SET DATA TYPE checks.

Tighten ALTER FOREIGN TABLE .. SET DATA TYPE checks.

If the foreign table's rowtype is being used as the type of a column in
another table, we can't just up and change its data type. This was
already checked for composite types and ordinary tables, but we
previously failed to enforce it for foreign tables.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=65377e0b9c0e0397b1598b38b6a7fb8b6f740d39

Modified Files
--------------
src/backend/commands/tablecmds.c | 43 +++++++++++++--------------
src/backend/commands/typecmds.c | 2 +-
src/include/commands/tablecmds.h | 3 +-
src/test/regress/expected/foreign_data.out | 7 ++++-
src/test/regress/sql/foreign_data.sql | 6 +++-
5 files changed, 34 insertions(+), 27 deletions(-)