[PATCH] cleanup hashindex for pg_migrator hashindex compat mode (for 8.4)

Attached patch cleanups hash index headers to allow compile hasham for
8.3 version. It helps to improve pg_migrator with capability to migrate
database with hash index without reindexing.

I discussed this patch year ago with Alvaro when we tried to cleanup
include bloating problem. It should reduce also number of including.

The main point is that hash functions for datatypes are now in related
data files in utils/adt directory. hash_any() and hash_uint32 it now in
utils/hashfunc.c.

It would be nice to have this in 8.4 because it allows to test index
migration functionality.

		Thanks Zdenek