Implemented parameter passing for function pointers

tests/programs/function-pointer-field.q

@@ -7,10 +7,10 @@ struct Struct {
 main() {
 	s := new(Struct)
 	s.func = f
-	s.func()
+	s.func(0)
 	sys.exit(1)
 }
 
-f() {
-	sys.exit(0)
+f(code int) {
+	sys.exit(code)
 }

tests/programs/function-pointer.q

@@ -1,13 +1,12 @@
-import core
 import sys
 
 main() {
 	func := f
-	func()
+	func(0)
 	sys.exit(1)
 }
 
-f() {
-	exit := core.exit
-	exit()
+f(code int) {
+	exit := sys.exit
+	exit(code)
 }