pgsql: Once again allow LWLocks to be used within DSM segments.

Once again allow LWLocks to be used within DSM segments.

Prior to commit 7882c3b0b95640e361f1533fe0f2d02e4e5d8610, it was
possible to use LWLocks within DSM segments, but that commit broke
this use case by switching from a doubly linked list to a circular
linked list. Switch back, using a new bit of general infrastructure
for maintaining lists of PGPROCs.

Thomas Munro, reviewed by me.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/b25b6c9701e5c18e3ad3b701df62380f8d138ba0

Modified Files
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src/backend/storage/lmgr/lwlock.c | 63 +++++++-------
src/include/storage/lwlock.h | 4 +-
src/include/storage/proc.h | 6 +-
src/include/storage/proclist.h | 154 +++++++++++++++++++++++++++++++++++
src/include/storage/proclist_types.h | 45 ++++++++++
src/tools/pgindent/typedefs.list | 3 +
6 files changed, 240 insertions(+), 35 deletions(-)