Improve Range Types and Exclusion Constraints example.

Make the examples self-contained to avoid confusion. Per bug report
8367 from KOIZUMI Satoru.
Revert WAL posix_fallocate() patches.

This reverts commit 269e780822abb2e44189afaccd6b0ee7aefa7ddd
and commit 5b571bb8c8d2bea610e01ae1ee7bc05adcfff528.

Unfortunately, the initial patch had insufficient performance testing,
and resulted in a regression.

Per report by Thom Brown.
Make catalog cache hash tables resizeable.

If the hash table backing a catalog cache becomes too full (fillfactor > 2),
enlarge it. A new buckets array, double the size of the old, is allocated,
and all entries in the old hash are moved to the right bucket in the new
hash.

This has two benefits. First, cache lookups don't get so expensive when
there are lots of entries in a cache, like if you access hundreds of
thousands of tables. Second, we can make the (initial) sizes of the caches
much smaller, which saves memory.

This patch dials down the initial sizes of the catcaches. The new sizes are
chosen so that a backend that only runs a few basic queries still won't need
to enlarge any of them.
Eliminate pg_rewrite.ev_attr column and related dead code.

Commit 95ef6a344821655ce4d0a74999ac49dd6af6d342 removed the
ability to create rules on an individual column as of 7.3, but
left some residual code which has since been useless.  This cleans
up that dead code without any change in behavior other than
dropping the useless column from the catalog.