functionObjects: Simplified the handling of the post-processing mode

Replaced the 'postProcess' argument to the 'write' and 'execute'
functions with the single static member 'postProcess' in the
functionObject base-class.

src/functionObjects/utilities/systemCall/systemCall.C

@@ -105,7 +105,7 @@ bool Foam::functionObjects::systemCall::read(const dictionary& dict)
 }
 
 
-bool Foam::functionObjects::systemCall::execute(const bool postProcess)
+bool Foam::functionObjects::systemCall::execute()
 {
     forAll(executeCalls_, callI)
     {
@@ -127,7 +127,7 @@ bool Foam::functionObjects::systemCall::end()
 }
 
 
-bool Foam::functionObjects::systemCall::write(const bool postProcess)
+bool Foam::functionObjects::systemCall::write()
 {
     forAll(writeCalls_, callI)
     {