pgsql: Remove rm_safe_restartpoint machinery.

Remove rm_safe_restartpoint machinery.

It is no longer used, none of the resource managers have multi-record
actions that would make it unsafe to perform a restartpoint.

Also don't allow rm_cleanup to write WAL records, it's also no longer
required. Move the call to rm_cleanup routines to make it more symmetric
with rm_startup.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/59a5ab3f426e74e3f901dc2cf533726bcea08ed2

Modified Files
--------------
src/backend/access/transam/rmgr.c | 4 +--
src/backend/access/transam/xlog.c | 50 +++++-------------------------------
src/include/access/rmgr.h | 2 +-
src/include/access/rmgrlist.h | 36 +++++++++++++-------------
src/include/access/xlog_internal.h | 1 -
5 files changed, 28 insertions(+), 65 deletions(-)