pgsql: Mark pg_stat_reset_shared as strict

Mark pg_stat_reset_shared as strict

This is the proper fix for bug #6082 about
pg_stat_reset_shared(NULL) causing a crash, and it reverts
commit 79aa44536f3980d324f486504cde643ce23bf5c6 on head.

The workaround of throwing an error from inside the function is
left on backbranches (including 9.1) since this change requires
a new initdb.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/24e2d4b6ba99985d5b710983714f0133e94dc343

Modified Files
--------------
src/backend/utils/adt/pgstatfuncs.c | 14 +++-----------
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_proc.h | 2 +-
3 files changed, 5 insertions(+), 13 deletions(-)