pgsql: Simplify use of AllocSetContextCreate() wrapper macro.

Simplify use of AllocSetContextCreate() wrapper macro.

We can allow this macro to accept either abbreviated or non-abbreviated
allocation parameters by making use of __VA_ARGS__. As noted by Andres
Freund, it's unlikely that any compiler would have __builtin_constant_p
but not __VA_ARGS__, so this gives up little or no error checking, and
it avoids a minor but annoying API break for extensions.

With this change, there is no reason for anybody to call
AllocSetContextCreateExtended directly, so in HEAD I renamed it to
AllocSetContextCreateInternal. It's probably too late for an ABI
break like that in 11, though.

Discussion: https://postgr.es/m/20181012170355.bhxi273skjt6sag4@alap3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/13cd7209f794d9dff8084c9748a78a0a5bf0464a

Modified Files
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src/backend/access/transam/xact.c | 10 +++++-----
src/backend/utils/mmgr/aset.c | 10 ++++++----
src/backend/utils/mmgr/mcxt.c | 10 +++++-----
src/include/utils/memutils.h | 13 ++++++-------
4 files changed, 22 insertions(+), 21 deletions(-)