pgsql: Silence another gcc 11 warning.

Silence another gcc 11 warning.

Per buildfarm and local experimentation, bleeding-edge gcc isn't
convinced that the MemSet in reorder_function_arguments() is safe.
Shut it up by adding an explicit check that pronargs isn't negative,
and by changing MemSet to memset.  (It appears that either change is
enough to quiet the warning at -O2, but let's do both to be sure.)

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1046dbedde2fc3fe55f007ff3255ab65ab98f858

Modified Files
--------------
src/backend/optimizer/util/clauses.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)