pgsql: Fix ALTER OPERATOR to update dependencies properly.

Fix ALTER OPERATOR to update dependencies properly.

Fix an oversight in commit 321eed5f0f7563a0: replacing an operator's
selectivity functions needs to result in a corresponding update in
pg_depend. We have a function that can handle that, but it was not
called by AlterOperator().

To fix this without enlarging pg_operator.h's #include list beyond
what clients can safely include, split off the function definitions
into a new file pg_operator_fn.h, similarly to what we've done for
some other catalog header files. It's not entirely clear whether
any client-side code needs to include pg_operator.h, but it seems
prudent to assume that there is some such code somewhere.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/0dab5ef39b3d9d86e45bbbb2f6ea60b4f5517d9a

Modified Files
--------------
src/backend/catalog/pg_operator.c | 35 +++++++-----
src/backend/commands/operatorcmds.c | 5 +-
src/include/catalog/pg_operator.h | 17 ------
src/include/catalog/pg_operator_fn.h | 34 ++++++++++++
src/test/regress/expected/alter_operator.out | 73 +++++++++++++++++++++++---
src/test/regress/sql/alter_operator.sql | 41 +++++++++++++--
6 files changed, 163 insertions(+), 42 deletions(-)