Use "foo(void)" for definitions of functions with no parameters.

Use "foo(void)" for definitions of functions with no parameters.

Standard practice in PostgreSQL is to use "foo(void)" instead of
"foo()", as the latter looks like an "old-style" function
declaration.  Similar changes were made in commits cdf4b9aff2,
0e72b9d440, 7069dbcc31, f1283ed6cc, 7b66e2c086, e95126cf04, and
9f7c527af3.

Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://postgr.es/m/aTBObQPg%2Bps5I7vl%40ip-10-97-1-34.eu-west-3.compute.internal