pgsql: Simplify index_[constraint_]create API

Simplify index_[constraint_]create API

Instead of passing large swaths of boolean arguments, define some flags
that can be used in a bitmask. This makes it easier not only to figure
out what each call site is doing, but also to add some new flags.

The flags are split in two -- one set for index_create directly and
another for constraints. index_create() itself receives both, and then
passes down the latter to index_constraint_create(), which can also be
called standalone.

Discussion: https://postgr.es/m/20171023151251.j75uoe27gajdjmlm@alvherre.pgsql
Reviewed-by: Simon Riggs

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a61f5ab986386628cf20b33971364475ce452412

Modified Files
--------------
src/backend/catalog/index.c | 105 ++++++++++++++++++++-------------------
src/backend/catalog/toasting.c | 3 +-
src/backend/commands/indexcmds.c | 33 +++++++++---
src/backend/commands/tablecmds.c | 13 +++--
src/include/catalog/index.h | 29 ++++++-----
5 files changed, 104 insertions(+), 79 deletions(-)