Add semantic patch to find void f() { ... return ((void)g())); ... }

When a function returns void, it can be used as an argument to return in
function returning also void, e.g.:

void in(void) {
  return;
}

void out(void) {
  return (in());
}

while this is legal, it should be rewritten as:

void out(void) {
  in();
  return;
}

The semantic patch just find the occurrences, and they need to be fixed
by hand.

cocci/return-void-from-void.spatch

@@ -0,0 +1,19 @@
+@ rule1 @
+identifier f1;
+@@
+
+void f1(...)
+{
+...
+}
+
+@ rule2 @
+identifier rule1.f1;
+identifier f2;
+@@
+
+void f2(...) {
+...
+* return(f1(...));
+...
+}