pgsql: Add transform functions for various temporal typmod coercisions.

Add transform functions for various temporal typmod coercisions.

This enables ALTER TABLE to skip table and index rebuilds in some cases.

Noah Misch, with trivial changes by me.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/c13897983a0006e658fb7c6410d72ca59fb87136

Modified Files
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src/backend/utils/adt/date.c | 11 +++++
src/backend/utils/adt/datetime.c | 35 +++++++++++++++
src/backend/utils/adt/timestamp.c | 86 +++++++++++++++++++++++++++++++++++++
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_proc.h | 16 +++++--
src/include/utils/date.h | 1 +
src/include/utils/datetime.h | 3 +
src/include/utils/timestamp.h | 2 +
8 files changed, 150 insertions(+), 6 deletions(-)