Because of gcc -Wmissing-prototypes, all functions in dynamically
loadable modules must have a separate prototype declaration. This is
meant to detect global functions that are not declared in header files,
but in cases where the function is called via dfmgr, this is redundant.
Besides filling up space with boilerplate, this is a frequent source of
compiler warnings in extension modules.
We can fix that by creating the function prototype as part of the
PG_FUNCTION_INFO_V1 macro, which such modules have to use anyway. That
makes the code of modules cleaner, because there is one less place where
the entry points have to be listed, and creates an additional check that
functions have the right prototype.
Remove now redundant prototypes from contrib and other modules.
This code is intended as a demonstration of how the dynamic shared
memory and dynamic background worker facilities can be used to establish
a group of coooperating processes which can coordinate their activities
using the shared memory message queue facility. By itself, the code
does nothing particularly interesting: it simply allows messages to
be passed through a loop of workers and back to the original process.
But it's a useful unit test, in addition to its demonstration value.
