Failing tests on Fedora

Hello, I started with running the testsuite recently, thanks a lot for its
existence!

There are currently 8 fails on my system (Fedora 20 x86_64), I didn't look
at all the errors carefully yet as I found in `git show a5e2002a` note
about expected failures — iirc, there is not specified what tests are
expected to fail.

Could we add one additional "EXP_FAIL" state for the testsuite to make
that clear?  Or at least have a list of expected failures somewhere?
(Also instructions how to run single test would be useful in README.txt).

Attached files (regression.out, regression.diffs).

--

I tried to look at the first FAIL so far.  Not sure what is the correct
fix-approach (maybe I face some misconfiguration) but VACUUM statement
does not seem to be candidate for PREPARE; none of STMT_TYPE_SPECIAL
statements actually.  So proposed fix is attached together with full
compressed "mylog" (+ patch with ignored indentation changes).

Pavel