pgsql: Make it easy to detach completely from shared memory.

Make it easy to detach completely from shared memory.

The new function dsm_detach_all() can be used either by postmaster
children that don't wish to take any risk of accidentally corrupting
shared memory; or by forked children of regular backends with
the same need.  This patch also updates the postmaster children that
already do PGSharedMemoryDetach() to do dsm_detach_all() as well.

Per discussion with Tom Lane.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/79a4d24f31e09eb3c421deb34829eee0bf6acd67

Modified Files
--------------
src/backend/postmaster/pgarch.c    |    2 ++
src/backend/postmaster/pgstat.c    |    2 ++
src/backend/postmaster/syslogger.c |    2 ++
src/backend/storage/ipc/dsm.c      |   27 +++++++++++++++++++++++++++
src/include/storage/dsm.h          |    1 +
5 files changed, 34 insertions(+)