Re: embedded list v2

Here's a prettified version of this stuff. I found one bug in the macro
ilist_s_head: the test was reversed. Also, curiously, the macro had the
same name as the struct, so I renamed the macro. I take it you haven't
used this macro, so maybe it shouldn't be there at all? Or maybe I
completely misread what the macro is supposed to do.

I also renamed all the structs and functions by changing ilist_s_foo to
Slist_foo. Similarly for ilist_d_foo. This is all mechanical so any
subsequent patch should be trivial to refresh for this change.

I think README.ilist (which is what you had in the comment at the top of
ilist.h) should be heavily expanded. I don't find it at all clear.

There were other cosmetic changes, but the implementation is pretty much
the same you submitted.

I didn't look at the other patch you posted, replacing dllist.c usage;
will do that next to verify that the list implementation works.

--
Álvaro Herrera http://www.2ndQuadrant.com/
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