[COMMITTERS] pgsql: Fix failure to remove dependencies when a partition isdetached.

Fix failure to remove dependencies when a partition is detached.

Otherwise, dropping the partitioned table will automatically drop
any previously-detached children, which would be unfortunate.

Ashutosh Bapat and Rahila Syed, reviewed by Amit Langote and by me.

Discussion: http://postgr.es/m/CAFjFpRdOwHuGj45i25iLQ4QituA0uH6RuLX1h5deD4KBZJ25yg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ee252f074b88e34ff7ac2b45a73d3cee12b1c671

Modified Files
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src/backend/commands/tablecmds.c          | 35 ++++++++++++++++++-------------
src/test/regress/expected/alter_table.out | 13 ++++++++++++
src/test/regress/sql/alter_table.sql      | 10 +++++++++
3 files changed, 44 insertions(+), 14 deletions(-)