Addition/dropping of inherited columns not handled properly

[jmafc]

Given tables test1 and test2, the latter inheriting from the former:

CREATE TABLE test1 (
    c1 integer NOT NULL,
    c2 text);
CREATE TABLE test2 (
    c3 date) INHERITS (test1);

If we add column c4 to test1, e.g., ALTER TABLE test1 ADD c4 char(5);, even though dbtoyaml flags c4 as inherited in test2, yamltodb generates two ALTER TABLES:

ALTER TABLE test1
    ADD COLUMN c4 character(5);
ALTER TABLE test2
    ADD COLUMN c4 character(5);

which as expected causes an error in Postgres: column "c4" of relation "test2" already exists.

Similarly, if column c2 is dropped from test1, .e.g., ALTER TABLE test1 DROP c2, yamltodb generates two drops:

ALTER TABLE test1 DROP COLUMN c2;
ALTER TABLE test2 DROP COLUMN c2;

Addding a default to the parent table, e.g., ALTER TABLE test1 ALTER c2 SET DEFAULT 'Some text', also causes two ALTER TABLEs to be generated by yamltodb, but PostgreS accepts those (but it's incorrect and inefficient).