Promote the Arg union to a core data type in Object.c such
that it is visible everywhere (many source files need it),
and correct declarations of several functions that use it.
The Process_sendSignal function is also corrected to have
the expected return type (bool, not void) - an error being
masked by ignoring this not-quite-harmless warning. I've
also added error checking to the kill(2) call here, which
was previously overlooked / missing (?).
Nathan Scott