Re: AllocSetContextCreate changes breake extensions

Re: Andres Freund 2018-10-12 <20181012170355.bhxi273skjt6sag4@alap3.anarazel.de>
> Hi,
> 
> Christoph Berg, on IRC, raised the issue that at least one extension
> failed compiling in v11. The extension currently does:
> https://github.com/pgq/pgq/blob/master/triggers/common.c#L225

Others have already been fixed, e.g. hll:

https://github.com/citusdata/postgresql-hll/pull/52/commits/e7bfbc80bbaca547167d645be11db24c8922385f

Andres' idea would enable the old code to continue to work, but
couldn't we additionally to backpatch the ALLOCSET_*_SIZES macros, so
the new code works also on old versions that didn't get the new
AllocSetContextCreate macro?

Christoph