Re: Error-safe user functions

OK, here's a v4 that I think is possibly committable.

I've changed all the comments and docs to use the "soft error"
terminology, but since using "soft" in the actual function names
didn't seem that appealing, they still use "safe".

I already pushed the 0000 elog-refactoring patch, since that seemed
uncontroversial. 0001 attached covers the same territory as before,
but I regrouped the rest so that 0002 installs the new test support
functions, then 0003 adds both the per-datatype changes and
corresponding test cases for bool, int4, arrays, and records.
The idea here is that 0003 can be pointed to as a sample of what
has to be done to datatype input functions, while the preceding
patches can be cited as relevant documentation. (I've not decided
whether to squash 0001 and 0002 together or commit them separately.
Does it make sense to break 0003 into 4 separate commits, or is
that overkill?)

Thoughts?

regards, tom lane