Making CallContext and InlineCodeBlock less special-case-y

As committed, gen_node_support.pl excludes CallContext and InlineCodeBlock
from getting unneeded support functions via some very ad-hoc code.
(Right now, there are some other node types that are handled similarly,
but I'm looking to drive that set to empty.) After looking at the
situation a bit, I think the problem is that these nodes are declared
in parsenodes.h even though they have exactly nothing to do with
parse trees. What they are is function-calling API infrastructure,
so it seems like the most natural home for them is fmgr.h. A weaker
case could be made for funcapi.h, perhaps.

So I tried moving them to fmgr.h, and it blew up because they need
typedef NodeTag while fmgr.h does not #include nodes.h. I feel that
the most reasonable approach is to just give up on that bit of
micro-optimization and let fmgr.h include nodes.h. It was already
doing a bit of hackery to compile "Node *" references without that
inclusion, so this seems more clean not less so.

Hence, I propose the attached. (The changes in the PL files are
just to align them on a common best practice for an InlineCodeBlock
argument.)

regards, tom lane