pgsql: Split heapam_xlog.h from heapam.h

Split heapam_xlog.h from heapam.h

The heapam XLog functions are used by other modules, not all of which
are interested in the rest of the heapam API.  With this, we let them
get just the XLog stuff in which they are interested and not pollute
them with unrelated includes.

Also, since heapam.h no longer requires xlog.h, many files that do
include heapam.h no longer get xlog.h automatically, including a few
headers.  This is useful because heapam.h is getting pulled in by
execnodes.h, which is in turn included by a lot of files.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/21c09e99dc252269360bd146afee9481fa80abbc

Modified Files
--------------
src/backend/access/gin/gininsert.c      |    1 +
src/backend/access/heap/heapam.c        |    1 +
src/backend/access/heap/pruneheap.c     |    1 +
src/backend/access/heap/rewriteheap.c   |    1 +
src/backend/access/heap/visibilitymap.c |    2 +-
src/backend/access/index/genam.c        |    1 +
src/backend/access/nbtree/nbtree.c      |    1 +
src/backend/access/nbtree/nbtsort.c     |    1 +
src/backend/access/nbtree/nbtxlog.c     |    1 +
src/backend/access/spgist/spginsert.c   |    1 +
src/backend/access/transam/rmgr.c       |    2 +-
src/backend/commands/tablecmds.c        |    2 +-
src/backend/commands/vacuumlazy.c       |    1 +
src/backend/executor/nodeSubplan.c      |    1 +
src/backend/foreign/foreign.c           |    1 +
src/backend/nodes/print.c               |    1 +
src/backend/optimizer/prep/prepunion.c  |    1 +
src/backend/optimizer/util/plancat.c    |    1 +
src/backend/parser/parse_func.c         |    1 +
src/backend/utils/adt/domains.c         |    1 +
src/backend/utils/adt/regproc.c         |    1 +
src/include/access/heapam.h             |   22 ---
src/include/access/heapam_xlog.h        |  264 +++++++++++++++++++++++++++++++
src/include/access/htup.h               |  219 -------------------------
src/include/commands/explain.h          |    1 +
src/include/commands/prepare.h          |    1 +
26 files changed, 287 insertions(+), 244 deletions(-)