pgsql: Remove belt-and-suspenders guards against buffer pin leaks.

Remove belt-and-suspenders guards against buffer pin leaks.

Forcibly releasing all leftover buffer pins should be unnecessary now
that we have a robust ResourceOwner mechanism, and it significantly
increases the cost of process shutdown.  Instead, in an assert-enabled
build, assert that no pins are held; in a non-assert-enabled build, do
nothing.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=c2281ac87cf4828b6b828dc8585a10aeb3a176e0

Modified Files
--------------
src/backend/storage/buffer/bufmgr.c   |   21 ++++++++-------------
src/backend/storage/buffer/localbuf.c |   21 +++++++++++++++------
2 files changed, 23 insertions(+), 19 deletions(-)