Re: automatically generating node support functions

Just one more thing here ... I really don't like the fact that
gen_node_support.pl's response to unparseable input is to silently
ignore it. That's maybe tolerable outside a node struct, but
I think we need a higher standard inside. I experimented with
promoting the commented-out "warn" to "die", and soon learned
that there are two shortcomings:

* We can't cope with the embedded union inside A_Const.
Simplest fix is to move it outside.

* We can't cope with function-pointer fields. The only real
problem there is that some of them spread across multiple lines,
but really that was a shortcoming we'd have to fix sometime
anyway.

Proposed patch attached.

regards, tom lane